Abstract: In this paper, a modular electronical chassis which cooled by air is designed. The heat dissipation effect is enhanced by fins and thermal expansion layer inside the Chassis. A three-dimensional theoretical model of flow and heat transfer inside the chassis is established. The influences of the angle, length of the flow baffle, the fins, and the wind speed on the heat dissipation of electronic devices are calculated and analyzed. The results show that when the wind speed increases from 1 m / s to 3 m / s , the node temperature decreases about 30oC. And the node temperature tends to be lowest when the flow baffle at the size of 150 mm and 120O. As a result, the increase of the length and angle of the flow baffle and the wind speed will enhance the heat dissipation of the chassis, and the fins and the heat pipe can also enhance the heat dissipation effect.