Abstract: Taking a priori precise ZPD derived from CORS network to augment PPP can reduce the number of unknown parameters,accelerate its ambiguity resolution in PPP and shorten the convergence time.We investigate the applicability and interpolation effect of spatial regression model in which precise ZPD derived from regional CORS network are used to interpolate ZPD for user site.We also demonstrate that H1QM3 model and MLCM model are equivalent,and propose the height constraint strategy to improve interpolation precision.It is shown that the H1QX1 model and H1QM3 model are superior to other models,interpolation precision is 10 mm in the flat region and 20mm in the undulated region.With height constraint,the precision of intepolated ZPD can be improved by 60% in the undulated region.The optimal number of reference stations for intepolation is 9 or 10.