Abstract: Abstract: The Chinese solar greenhouse is a low carbon and energy-saving greenhouse structure, but it has an issue of energy imbalance between daytime and nighttime. Due to the surplus air heat energy, the solar greenhouse has to be ventilated in the daytime which leads to a large heat loss. However, cold damages and plant diseases and insect infection caused by low temperature and high humidity occur during cold winter night. In order to achieve transferring heat energy in terms of time and space inside the solar greenhouse, and then improve the utilization efficiency of surplus air heat energy, finally avoid low temperature in the greenhouses, a solar greenhouse surplus air heat pump heating system (SAHPHS) for the solar greenhouse was designed. In the daytime, air heat energy inside the solar greenhouse was pumped by the SAHPHS and stored in the heat reservoir. When indoor air temperature fell below the optimum range for crops in the nighttime, centrifugal fan and circulating water pump were started and heat energy stored in the heat reservoir was released directly via surface air cooler of the SAHPHS. As water temperature of the heat reservoir decreased to a certain value, the SAHPHS with a reverse operation was used to continue releasing heat energy forcibly. In addition, centrifugal fan and fin type electrical heater were used for emergency heating when encountering overcast weather for several days or extremely low air temperature. Tests for the SAHPHS were carried out from 10 Dec. 2014 to 10 Feb. 2015 and the effectiveness of the system was studied. The results showed that during running period of the SAHPHS, average air temperature inside the greenhouse was 2.8 to 4.4℃ higher than that in a comparable greenhouse in the nighttime, and the relative humidity decreased by 8% to 11.5%. Meanwhile, compared to the similar greenhouse without such system, average air temperature inside the greenhouse decreased by 3.7 to 5.2℃ and the relative humidity decreased by 12.3% to 16.5% during the daytime. So the SAHPHS not only had remarkable effects for heating and dehumidification in the nighttime, but also for cooling and dehumidification in the daytime. Air temperature in east-west direction inside the experimental greenhouse was found to be evenly distributed during heat collecting period in the daytime and heat releasing period in the nighttime with heat pump cycles, but have significant differences during heat releasing period with the usage of surface air cooler in the nighttime. Meanwhile the SAHPHS was found to have significant effect on raising daily average soil temperature in a depth of more than 20 centimeters. Heat collecting power of the SAHPHS was 12.5 to 16.4 kW, and coefficient of performance ranged from 3.3 to 4.2 during heat collecting period in the daytime. Heat releasing power of the SAHPHS was 9.3 to 10.3 kW, and coefficient of performance ranged from 6.6 to 7.4 during heat releasing period with the usage of surface air cooler in the nighttime. Coefficient of performance of the SAHPHS ranged from 3.8 to 4.1 with the SAHPHS running in a reverse heat pump cycle during heat releasing period in the nighttime. The SAHPHS was always under heating conditions in both heat collecting and heat releasing period. The coefficient of performance of the overall system in heating cycles reached 2.7, showing energy-saving effect. The SAHPHS had good application effects in heating, dehumidification and energy conservation, and this study would provide a new idea for the Chinese solar greenhouse energy-saving heating in the nighttime.