Burn-in test is helpful to improve the reliability of Integrated Circuit (IC). It can screen the early failures of the IC and get a good quality. When the IC technology enters deep sub-micron technologies, the increased standby leakage current will cause the higher junction temperature. The high junction temperature in the CMOS circuit may lead to thermal runaway and yield loss during burn-in test. It is a challenge to keep a uniform temperature in the burn-in system. In this paper, a modified burn-in socket and a fuzzy control structure are proposed to solve the non-uniform temperature in the burn-in system. First, a burn-in socket, which has a heater to raise the temperature and a fan to lower the temperature, is proposed and implemented. Using the modified socket, every Device Under Test (DUT) has its own temperature control system. Then, a fuzzy control structure is proposed to control the heater and fan to adjust the temperature of the DUT. From the experiment, the implemented burn-in system has a fast response time and an excellent dynamic balancing.