Abstract: This paper deals with the effects of conservation of mass and discrepancy of cotidal charts on Loading tidal computations, and handles the spherical harmonic model of the main constituents of ocean tide.The numerical results show that it is necessary to modify schwiderski's glodal 1°×°1 cotidal data using much detailed costal cotidal data while computing ocean loading tidal effects in the mainland of China. Meanwhile, correction of mass conservation should be applied to the cotidal data The accuracy of tilt loading tide computed by means of integral technique in the inner zone and spherical harmonic expansion in the outer area is about 0.04ms.