Abstract: The least-squares collocation harmonic analysis method, which is used to determine the earth geopotential coefficients from the radial satellite gravity gradient, is deeply studied. The principle of the least-squares collocation is firstly dissertated, and the covariance and self-covariance matrix between the disturbing gravity gradients and spherical harmonics are derived. When the disturbing gravity gradients are in the regularized equi-longitude grid, the covariance matrix between geopotential and disturbing gravity gradients has the configuration of blocked Toeplitz circulation matrix, and its degree can be lowered by using the fast Fourier transform technology effectively. Truncated singular value decomposition (TSVD) which is used to solve the ill-posed problem of covariance matrix is studied. The complete formula of least-squares collocation harmonic analysis of the radial gravity gradient is finally obtained. The simulation experiment results show that the least-squares collocation harmonic analysis based on TSVD can recover the global gravity field in a rather high precision and validity and practicability of algorithms in this paper are also testified.