Abstract: eat production and heat dissipati on of astronauts during space flight are important parameters for engineering design of life support system as well as for judgement of their work loads and arrangement of work-rest rule.In conjunction with our early experiences and current literature,this paper introduced three methods for estimation of astronallts'metabolic rate.The mr heat production both in vehicular and in extravehicular activities were summarized and the causes of metabolic variat cons comprehensively analyzed. Discussion is stressed on the factorsinfluencing heat exch ange of space garment in hypobaric envir onmentsin order to convert the garment flow rate(STP)obtained in ground experiments into the equivalent flow rate for removing the same heat fromthe garment at various altitudes.