Abstract: In this paper, the calculation methods of the effect of oceanic tides (M₂) on the gravity tidal observations are discussed. The global oceanic area is divided into two parts: the near area and the far area. In the near area, the numerical integration method with Green function is adopted. In the far one, convolution integration is used for the g^N (θ), while a spherical harmonic expansion in which the function series is fitted with the globel oceanic tide height is used for the g^E(θ). Finally, the corrections of the effect of oceanic tides on the gravity tidal observations in Beijing, Lanzhou and Lasa were calculated.