Abstract: In order to satisfy the observation of the astronomical imaging system of 1.2m telescope, a programmable thermostatic filter wheel box based on an STM32 MCU is introduced. The box has three wheels, which can be driven by their respective motor, and 15 optical filters can be switched at most. In order to avoid wavelength drift of the filters, a heat preservation system driven by PID temperature control algorithm is designed to keep temperature stable inside the box. A computer can communicate through serial port with an electronic control box, which is responsible for direct driving for the wheel motor and the heating. In summary, the system is compact-sized with secure electronic control circuit, and fully functioning MCU software. At the end of this paper, results of test show that when it is in the constant temperature mode, the wheel box works well below -25℃, keeping the temperature inside within ±1℃ around set temperature, and it costs 10s at most to switch filter once.