Energy consumption of China increases rapidly due to recent economical development. That is one of major reasons of air pollution problem in large cities of China. Energy consumption of residential sector shares 40% of the total consumption and also increases. In residential buildings of developed countries, energy consumption used for space heating plays an important role in total residential energy consumption. Therefore, in order to estimate the future trend of residential energy consumption in China, it is necessary to understand the saturation level of space heating equipment and indoor thermal environment. However, there is no data available of these matters. Then, this paper deals with the space heating and indoor thermal environment of residential buildings in Shanghai and Beijing. The investigation has been done for 150 houses in winters of 1998 and 1999 by means of questionnaire and liquid crystal thermometers. Also, the temperature and humidity of 15 houses were measured by small data loggers with temperature and humidity sensors. The findings are as follows: 1) In Shanghai, the air conditioning unit is popularly used for space heating in 45% houses. One or two rooms of the house is only heated for about 4 hours in the evening. The indoor temperature of the houses was around 15°C and was stable during the measurement period due to thermal capacity of concrete structure. Occupant wares relatively heavy clothes in low temperature indoor environment. 2) In Beijing, the central space heating is popular and all rooms are heated in whole days. The room temperature is around 20°C.