In order to develop an automatic guidance system for orchard machinery, laser navigation method was used on an orchard tractor .A laser scanner was used to collect the real time information of fruit trees’ location and a path planning program was developed based on the least square method. A proportional controller was designed with the information of course deviation and lateral deviation as its input and the speed of steering motor as output to navigate the tractor moving straightly. The system realized the control function of navigating the tractor to move in a straight line in alleyways of the orchard. The maximum lateral deviation was 0.15 m after the tractor moved 30 m path at the speed of 0.27 m/s. Test results indicated that the system could be applied to the automatic navigation of orchard machinery and had certain reliability.