Satellite altimeter was widely used in ocean monitoring and research, in order to find out the actual performance of the altimeter and access the accuratesea level data, we need to calibration. GPS buoys was mainstream devices in altimeter absolute calibration. Through simulation and experiment about the self-developed GPS buoy, this paperstudied the precision of GPS bouy and factors affecting.The results show that the self-developed GPS GPS buoy elevation measurement precision can reach 1 cm, meet the altimeter sea surface height calibration requirements.