Abstract: Both the relative and absolute models of antenna phase center(IGS_01 and IGS05) are described.Influence of these two models on PPP estimation,including coordinates,Zenith path delay(ZPD) and receiver clock biases are analyzed.Results show that the difference of ZPD estimates is about 5 mm,and that of estimated receiver clock bias and height of site is relatively around 3 ns and 1 cm,respectively,based on different antenna phase center models.In addition,with the absolute model,the accuracy of PPP-derived ZPD is better than 5 mm,and the horizontal positioning accuracy arrives at 1 cm,while the accuracy of estimated clock bias is about 0.1 ns.