Focusing on the study of indoor thermal environment under the air distribution of low supply and middle return in large spaces,an energy balance equation and mass balance equation were built to analyze each module in order to get the air temperature in multi-node.Experimental verifications for the calculation results of four working conditions were carried out by using the scale model of a large space laboratory.As shown by the results,the absolute value of maximum error between theoretical and experimental values of air temperature in respective areas is 3%,and the average error is 1.4%.