Natural rubber was compounded with activator, sulfenamide accelerator, sulfur and chemical blowing agent in an internal mixer at 60 rpm of screw speed for 10 minutes. The amount of azodicarbonamide, a low priced chemical blowing agent, was varied at 0, 3, 4, 5 and 6 phr. The cure kinetic of rubber compound was studied by means of moving die rheometry (MDR). The cure time from MDR at 155 oC was used in compression process for specimen preparation. The torque from MDR was analyzed and converted to degree of cure from the difference between the maximum and minimum torque. After compression at 155 oC, bubbles and foam structure of natural rubber foam was characterized by means of scanning electron microscopy (SEM). Finally, the thermal behavior was evaluated by means of thermo-mechanical analysis (TMA) for understanding the effect of chemical blowing agent on thermal expansion of specimen which was the important factor of natural rubber foam when using in automotive industries.