The obstacle avoidance system is an important part of the intelligent inspection robot. According to the special environmental requirements for substation inspection robot, the inspection robot obstacle avoidance detection system was designed. The system takes MCU as the controller core, selects many sets of ultrasonic sensors to detect the obstacle information around the robot, designs the transmitting and receiving circuit of the ultrasonic signal, and completes the system software program. In consideration of the substations effect of EMI to the electronic equipments, when designing circuit, using a large of filter circuit, improve systems anti-interference performance, realize real-time and veracity of measurement. Using on substation shows that the system run steadily, have high measurement precision, its important for improving the robot using on substation.