This paper intends to explore the indoor thermal environment's influence on human comfort and health in a physiological approach, for which purpose, 50 normally-dressed healthy volunteers, aged from 20 to 58, have been selected for the designed physiological test and questionnaire survey, in a natural winter indoor environment in Chongqing, with the indoor temperature between 8.2-16.2°C, relative humidity 60-90% and air velocity 0.02-0.08m/s. Based on the test, it is concluded that under the condition of reasonable warm clothes, the value of human sensory-nerve conduction velocity (SCV) decreases as time goes on, and began to maintain unchanged at a lag of 60 minutes. And based on the questionnaire survey, it is analyzed that under a comparatively cold environment like 10°C or 13°C, the subjects’ sensation of coldness increases after 60 minutes of test, which makes the author judge that these subjects’ physiological adaptability has achieved its limit in such a cold environment after such a length of time, and their health would be negatively affected if stayed in such an environment continuously. Therefore, this research is capable of scientific support for definition of acceptable indoor thermal environment.