Abstract: In the context of the increasing importance on environmental control in large-scale pig farming operations, more attention is being given to the research on different environmental impacts on pig health. In order to conduct variable environments for pig health experiments, a pig breeding chamber under multiple environment variable control was designed in this paper for more precise environmental control experiments. The pig breeding chamber was composed of 4 parts, the main chamber, the air mixing box, the environmental regulation executing devices, and the environmental control system. The main chamber was the living space for experimental animals. The air mixing box was used to regulate the air variables, such as temperature, relative humidity, NH3 and CO2 concentration, before the air entering the main chamber. The environmental regulation executing devices involved the fans, the air valves, the air conditioning compressor, the air heating pipe, the electromagnetic valve for NH3. Then the environmental control system read environment variables through sensors and controlled the working of all the environmental regulation executing devices to limit the environment variables in the main chamber in a setting range. Main ventilation mode of the pig breeding chamber was self-circulated. A fan working at the outlet built a negative pressure to exhaust the airflow entering the main chamber through the air mixing box and the ventilation pipe. The air flow entered the main chamber through three air inlets, dissipated in the chamber and then was exhausted from the outlet, thereby forming the air circulation. The air conditioning compressor and air heating pipe in the air mixing box could cool down or heat up the airflow respectively, and the electromagnetic valve for NH3 gas could increase NH3 concentration of the airflow. The exhaust air valve was working with the fresh air valve to reduce NH3 concentration or CO2 concentration in the chamber. The airflow in the main chamber was optimized previously by ANSYS flow field simulation. The environmental control system of the chamber was composed of environmental variable detection module, S7-200 PLC (Programmable Logical Controller), and host computer. The environment variable detection module sampled all the environmental data, such as temperature, relative humidity, air velocity, NH3 concentration, and CO2 concentration, and sent to a STM32 microcontroller every 2 seconds. The program embedded in STM32 integrated these data into one data packet and sent them to the S7-200 PLC through a serial port. The S7-200 PLC transferred the data to the host computer and simultaneously calculated out control instructions to control environmental regulation executing devices, limited the chamber’s internal environments to a setting range. Besides, the manure pump and LED lights were also controlled by the PLC to realize automatic manure cleaning and lighting timing. The host computer realized dynamic and real-time display and storage of environmental data. The running states of the executing devices were showed on the screen through WinCC monitoring software. Three tests for the pig breeding chamber were conducted, including the smoke test for air flow field, an empty chamber test and a full-loaded chamber test. The smoke test of air flow field verified the airflow pattern, which was simulated by ANSYS previously. Result showed the smoke formed a circle in the main chamber and dissipated all through the chamber without leaving any dead space. The test in the empty chamber verified the function and performance of the control system. The results of the environmental test with animals loaded showed that the control precision of temperature was limited within ±1℃, the relative humidity could be controlled within the pig comfortable range of 50%-80%, the oscillations of NH3 concentration were limited less than ±3×10-6 when the setting value of NH3 concentration was 10×10-6, and the concentration of CO2 could be controlled below 1 540×10-6 basically, which was a standard for animal health. During the full-loaded experiment, which lasted for almost 3 weeks, temperature, relative humidity, NH3 and CO2 concentrations variables inside the chamber were accurately controlled. This shows the pig breeding chamber can provide an effective platform for more precise pig, especially nurseries, breeding experiments under variable environments and potentially helps improve the research method to reveal the relationship between pigs and their environments.