Abstract: Temperature control is an effective way to realize the total internal cavity diode-pumped Nd:YAG microchip laser. How to provide effective means of temperature control for Nd:YAG microchip laser was studied. The temperature control accuracy needed was within the fluctuation range of 0.09 ℃. Based on this designed goal, the design process of each key link was presented. By means of frequency domain analysis, the characteristics of the temperature control system was analyzed and adjusted. By theoretical calculation, the system was remolded into an optimal model for second-order system and the theoretical analysis was verifiedby experiments. The temperature control system was designed for the total internal cavity diode-pumped Nd:YAG microchip laser, which guaranteed the temperature of the microchip can be set arbitrarily between 18 ℃ and 38 ℃ within the fluctuation range of 0.05 ℃ under normal condition (around 26℃). The system can also guarantees the temperature of the microchip can be set at 24 ℃, within the fluctuation range of 0.05 ℃, under arbitrarily temperature condition between 18 ℃ and 27 ℃.