Abstract: Nighttime indoor air temperature is one of the most important indicators for structural renewal and environmental control in Chinese solar greenhouses (CSGs). It is often required for the thermal contribution of heat transfer to the air temperature at nighttime. In this study, a qualitative analysis was conducted on three events influencing the nighttime air temperature: convective heat transfer between surfaces and room air, condensation on the south roof surface, and cold air infiltration between the interior and exterior. Three typical CSGs were also selected: the strawberry, the tomato, and the empty greenhouse. Specifically, the strawberry/tomato and empty greenhouses were used as 8 and 12 m spans, respectively. The strawberry and tomato greenhouses were employed for soil and substrate cultivation, respectively. The outdoor parameters were measured, including solar radiation, air temperature, relative humidity, and wind speed, whereas the indoor ones included air temperature, relative humidity, and surface temperatures. All the indoor surfaces were contacted directly with the room air, such as the surfaces of the north wall, north roof, south roof, soil ridge, soil furrow, and the crop leaf. The heat transfer was calculated for the south roof condensation and the indoor-outdoor cold air infiltration. The convection coefficients were derived for the convective heat transfer between the north wall and the ground surfaces and the air. The results showed that the largest sensible heat supply was the convection heat release to room air at night from the ground (ridges and gullies for cropped CSGs). The convection heat values were 63 and 55 W, respectively, for the unit length of the strawberry greenhouse on sunny and cloudy days from 18:00 to 07:00 the next morning; The tomato greenhouse averaged 53 W for sunny and cloudy days; While the empty greenhouse reached 145 and 120 W for sunny and cloudy days, respectively. The average convective heat release from the north wall surface was relatively low on sunny days. The strawberry, tomato, and empty greenhouse were 26, 24, and 15 W, respectively, where the average convective heat release on cloudy days was roughly half that of sunny ones. Averaged convective heat released from ridges and gullies at night on sunny and cloudy days in cropped greenhouses accounted for 50% of the total average convective heat release, while that from the ground of the empty greenhouse accounted for 90% to 95% on sunny or cloudy days. The averaged convective heat released from the crop canopy at night contributed about 30%-50% heat supply. The maximum heat loss at night was the convection or the condensation from the south roof. The findings can be expected to determine the key influencing factors of greenhouse nighttime air temperature.