A new sun-tracker based on a PSD sensor is developed.Two stepper motors are used to achieve the track of sun.It can achieve the track under any kind of weather and light-electric track is used in sunny day

and calendar-check track in rainy day.It can realized the automatic tracking in any direction angle of 360°and any height angle of 90°.Analysis of the system error and some experiments are done

experiment results show that the accuracy of this sun-tracker can be limited in 0.1° in ±12° inspect angle.This device can run stably under all weather.