A design of high precision multiple channel temperature controller was introduced. By using 16 bit high speed AD7705 and ARM processor, signal of temperature from multiple channels was collected effective in turn. PWM control signal was calculated and output using integral separated PID algorithm. The on-off time of heater was controlled using solid state relays, which make temperatures of each channel approach the presetting value and fluctuate in allowed range of control accuracy. Simultaneous control of multiple temperature controllers was realized with only one upper computer through Modbus protocol.