Clothing thermal resistance is a key factor that affects the thermal comfort of human body. The total thermal resistance of bedding and clothing system in sleeping at night includes the clothing system resistance and the body of the mattress system. In the low pressure environment, there is still a lack of experimental data and calculation model of thermal resistance, with no reference to theory models. In this paper, based on calculation method of the total thermal resistance of bedding and clothing system in sleeping, the calculation model of total thermal resistance in low pressure environment is established by the introduction of pressure correction of related parameters. The typical total thermal resistance both summer and winter is calculated using the model. The variation rules of total thermal resistance caused by the pressure reducing is obtained. At altitude of less than 3000m, the increasing coefficient of total thermal resistance of bedding and clothing system caused by the coverage ratio of blanket is not more than 0.05. The total thermal resistances both winter and summer increase with atmospheric pressure decreasing. There is a same maximum percentage of 42% under the condition of 23.3% of blanket coverage.