To analyze the impact of season on human thermal adaptability and the influence of cold radiation from window in winter on human local thermal sensation, a field study on indoor thermal environment, thermal sensation and thermal comfort in classrooms at a university in Harbin during the heating period in winter and spring was conducted. The environment parameters were tested and at the same time the subjects’ thermal sensation were undertaken. The results show that the neutral temperature is close to the indoor average temperature during winter. The neutral temperature is obviously lower than the indoor average temperatures during spring. In warmer climates, the subjects felt warmer in winter than that in spring. This shows that people in Harbin has fully adapted to the indoor and outdoor thermal environment in long-term cold winter. If the indoor air temperatures are kept too high in winter, people will feel more uncomfortable. The human adaptability to thermal environment should be made full use of by reducing the indoor temperature during winter and spring to improve comfort and save energy for heating. The subjects nearby the window feel colder than the control group subjects. The occupants often feel cold at their shoulder and back, and feel comfortable at their head. The adaptive measures taken by the subjects include opening doors or windows, increasing or decreasing clothes, etc.[JP]