Recently, electronic systems including computers have been rapidly shrinking in size while at the same time the complexity and the capability of these systems continue to grow/sup [1]/. Thus, system volumes have decreased as system power has increased, resulting in dramatic increases in system heat density. The high temperature of the computer system is considered as the major reason for low performance and shortening life of the product. It is necessary to solve this problem due to the heat density increased and to develop the design skill of the computer cabinet according to miniaturization. M4500 desk-top computer was selected for analyzing the thermal management inside cabinet. The cabinet volume, the configuration of the heating devices, the size and location of air ventilation, and the fan selection have been investigated as the important parameters to find out an optimal cabinet design. The objectives of this project were to analyze which design parameters would affect cooling performance by thermal strategy, to design an optimal model, and to measure the temperatures of the main parts to confirm the effect of the thermal design. The temperatures of each part of the optimal model were compared with those of the existing model. As a result. the volume of this miniaturized model was about 16% smaller than that of M4500 without any change in operating performance.