This paper presents the design of a smart car based on STC89C51 MCU, which can avoid obstruction, track and be remotely controlled. The photoelectric switch can detect barriers, and carry out it by driving the motor steering. The infrared sensors can find the line and let the car ran from it. Using infrared signal, the car can also be remotely controlled to forward, back, turn right, turn left, stop and start. The car includes the chassis, the sensors and the vehicle electric circuits. The electric circuits includes the batteries, the MCU and the driving part. The overall system ulilizes modularization designing, which is simple, but reliable.