A full automatic control method of CI-SR800 blackbody based on digital bridge is proposed to allow the blackbody to access the full-automatic test line without affecting the original using method. According to the 4 wire resistance touch screen and an internal buzzer used in CI-SR800 blackbody, the digital bridge circuit and the buzzer detection circuit are designed. A series of design are carried out, in consideration of the requirement of the construction operability and appearance at the same time. 4 wires of the touch screen and 2 wires of the buzzer through the IO interface reserved by the blackbody controller are led in parallel method. A control circuit for the blackbody is designed based on practical working principle of the blackbody man-machine interface. The practical applications show that the design is easy to install, maintenance free and stable in operation.