This paper presents the study on the cooling performance on inverter controller of domestic air conditioner. The performance of heat sink attached to the inverter controller is highly influenced by the ambient condition and the layout of the neighboring parts. The numerical analysis has been used for the parameter study influencing cooling performance of the heat sink. The thermal resistances from CFD results were compared against to those of two reference experiment results. CFD and experiment results show good agreement in improvement ratio of thermal resistance. Among the parameters studied, the heat sink location was found to be most effective parameter on the heat sink cooling performance with 23% improvement. The condenser height change and PCB cover modification have resulted in cooling performance improvement of 16.2% and 8.4%, respectively.