Abstract: Simplification of mathematical modelling and uncertainties of physical parameters which cause the difference between experiment data and numerical results calculated by thermal network method are discussed. To improve the accuracy of analytical predictions, it is necessary to correct the thermalnetwork by experiment data. The difficulties of correction are too many coefficients needed to be corrected.the small temperature difference among nodes and no experiment data at some nodes.A new method to deal with these difficulties is developed in this paper. The method simplifies the radiation relationships of mathematical model, and uses Least Square Estimation to produce a more practical mathematical model. The themal network of a spacecraft compartment is corrected by this method.