This research uses the advanced simulation tool FloTHERM to study the effects of different opening ratios of the front panel to temperature field in the micro-desktop. Based on the studies, the best opening ratio with better cost performance and lower temperature is selected. Simulation results match experimental data well. Micro-desktop is a new smaller volume product with higher integration, which leads to smaller space for internal components and higher flow resistance inside. Therefore, the opening ratio of the front panel strongly influences the flow from internal fan at specific speed. Hence, this will further determine surface temperature distribution of important components and product performance. However, a larger opening ratio might also cause problems to structural strength and safety. This paper calculates flow fields and temperature fields inside the enclosure at different opening ratios, evaluates correlation between opening ratio and temperature of important components under different ambient temperatures, and selects the best solution where the system operates the most cost effectively. The simulation results are compared with experimental data to verify the validity of simulation calculation.