Abstract: A cold plate(CP) of small volume and high heat flux for cooling high power electronic equiments was designed and experimented, which has only one layer of fins and is less than 5 mm thick. Coolant circulates properly when Re is under 100 in the system consisting of CP, pumps, refrigerator, chokes, etc.. An one dimensional numerical model was obtained to describe the performance of CP working under steady heat tranfer and steady flow. The theory is compared with the experimental data recently obtained. The agreement between the model prediction and the experimental result is very good.