For exact analysis of cooling ability of thermoelectric cooling system, accurate extraction of thermophysical parameters is of vital importance. Cooling capacity is the measure of system′s cooling ability. Based on the datasheet of thermoelectric module and empirical formulas evaluating temperature-dependent parameters, performance curves assuming constant and temperature-dependent material properties were plotted respectively. The standard value of cooling capacity and performance curve were obtained with differential equations for energy conservation along the TE element. Through numerical comparison and analysis, it was found that the maximum absolute error of cooling capacity was 6 W for constant parameters estimated from the datasheet and could be minimized by applying a proper set of constant parameters. The maximum absolute error of cooling capacity was 1.5 W for temperature-dependent parameters calculated with empirical formulas. The accuracy of the numerical model assuming temperature-dependent material peoperties was confirmed and it could be used to accutately evaluate thermoelectric cooling performance.