Based on the structure and coupling characteristics of semiconductor thermoelectric cooler，the expression of inner heat source is simplified through separating the responding area of Peltier effect and Joule effect，and a new heat conduction model of thermoelectric cooler is established with the help of elliptic partial differential equation．This model is independent of the physical and geometrical parameters of the thermoelectric couple，and it only needs the standard parameters provided by the producer，so that the numerical analysis of temperature field of nonuniform heat flow can be realized at given current and boundary conditions． Then，the universality of the proposed model is verified by fitting manufacturer’s data． Moreover，with the help of this model，the three-dimension and sectional temperature field distributions in the heat dissipation system of small-size semiconductor power devices with thermoe-lectric cooler are obtained，and the common characteristics of such heat dissipation system is revealed．