This paper introduces the accurate pointing and auto-unlocking sun tracker on the Fengyun-3(FY-3, C)satellite designed by ourselves. The auto-unlocking sun tracker is rotating around the biaxial tracking platform, consisting of a drive unit, an encoder, a sun sensor, mechanical positioning elements etc. It realizes the on-orbit pointing strategy by both active routine and passive redundancy. In order to avoid the influences of vibration and shock in transporting and launching the satellite on the performance and lifetime of the satellite, the pointing device has a degree of freedom for locking and releasing function, and achieves the function that locking freedom before the launch and releasing freedom after the launch. The paper describes the structures of the pointing device, the design process of precise pointing and the result of life test. FY-3 (C) was successfully launched in October 2013. the sun tracker of solar radiation monitor has unlocked successfully when it was into the orbit. It has run continuously for 17 months in the orbit, and showing the orbit pointing accuracy within ±0.05 °. The tracker loaded the solar radiation monitor has accessed a large number of high precision and valuable solar radiation data. The accurate pointing and auto-unlocking sun tracker provides foundation for FY system satellites and other satellite loads in design of pointing devices.