Abstract: In order to solve the problem of low automaticity and high experimental error in the current feed nutrition evaluation approaches for ruminants, an automated gas production recording system for In Vitro fermentation based on virtual instrumentation was developed. The newly designed apparatus makes use of electronic pressure switch in combination with electromagnetic valves to release overpressure inside In Vitro fermentation container during the incubation. In this very sensitive system, no gas accumulation and pressure accumulation take place. Each vent of valve opening represents a certain amount of gas, set at about 1.0～2.8 mL. By recording the vents of valve openings in time, an In Vitro gas production can be recorded, analyzed and saved automatically. With satisfactory automation, intelligence and graphics as the experiment results show that the system has higher accuracy, higher repeatability and efficiency for the real-time test results, and can significantly reduce the workload of scientific researchers in feed evaluation. Through gas sample analysis, the system can be used for evaluation of greenhouse gas, such as methane and carbon dioxide, emitted by in vitro fermentation mainly by domestic ruminants.