Thermal management of rotating electric machines is a very important area for maintaining the high durability, reliability, and safety of each machine. BLDC motor has advantages of low noise due to brushless structure, easy to accelerate, high durability, and reliability. However, the use of high power for a long time and unbalanced thermal management increase the temperature in the motor. It increases the resistance of the cooper winding and decreases the performance of permanent magnets. In this study, the experiment equipment consists of a dynamometer, a thermos-hygrostat, and a 600W BLDC motor for the experimental test of temperature rise. The air-cooling system is applied to analysis the temperature rise of copper winding and motor efficiency according to the inlet flow rates. This study investigates the correlation between the temperature rise of copper windings and the efficiency of the motor.