Multilayer thermal insulation is one of the most used spacecraft thermal control systems. In this case a problem of extracting maximum information about system condition from data obtained during spacecraft thermal testing becomes actual. It’s necessary to create a mathematical model describing a real, not ideal, system to determine the insulation performance with better accuracy. For example, currently the insulation models did not take into account such phenomenon as a near-field heat transfer. This type of radiative heat transfer can make a significant contribution to a heat flux between insulation layers, that is especially important for cryogenic systems. In the presented work, one of the ways to improve the mathematical model of multilayer thermal insulation is considered. It includes not only radiation and conductive components but also a heat flux caused by non-propagating electromagnetic waves, that will allow to increase the heat calculation accuracy for a varying insulation density.