A laser navigation system is designed to guide the weeding robot，so that the robot can complete the weeding work according to the fixed direction. The laser launching module is fastened in the guiding destination, including laser modulation circuit and a laser source. There is a photoelectricity detector in the front of the weeding robot, composing of photocells array and multichannel gathering circuit. Laser launching device communicates with the robot by wireless send-receive module. The photoelectricity detector detects the position of the light spot when the laser coming from the laser launching device shines photoelectricity detector, then the ARM can calculate for the robot’s position information which will guide the robot moving straightly to the destination automatically.