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Abstract: The pre-mission certification of the irregular- shaped asteroid gravitation is essential for the orbit design (in orbiting phase or landing phase). This paper proposes a novel algorithm for the irregular-shaped asteroid spherical harmonic coefficient estimation, where the gravitation potential of the asteroid is reconstructed using the polyhedral model method and is taken as the virtual measurements. Then a formula for the relationship between the spherical harmonic coefficients and the gravitation is suggested. Finally the spherical harmonic coefficients of the asteroid gravity are computed by solving the over-determined equations based on the least squares method (LSM). Compared with the traditional method which approximates the asteroid as a tri-axial ellipsoid, the algorithm proposed in this paper could obviously improve the asteroid gravitation modeling resolution. When compared with the spherical harmonic coefficients of Eros 433 derived from NEAR probe orbit data, the relative error is less than 6%. The result indicates that it is more accurate and will offer more information for pre-mission orbit design.