A spherical aberration compensation method is provided. A first thickness of a cover layer at a first radius position of an optical disc is measured. A second thickness of the cover layer at a second radius position of the optical disc is measured. A spherical aberration calibration is performed at a third radius position of the optical disc to obtain an optimal spherical aberration compensation value. According to the first and second radius positions, the first and second thicknesses, and the optimal spherical aberration compensation value at the third radius position, a spherical aberration compensation formula is acquired. Afterwards, an updated spherical aberration compensation value is calculated by the spherical aberration compensation formula according to a fourth radius position where an optical pickup head of the optical disc drive is located. The updated spherical aberration compensation value is inputted into a spherical aberration compensator of the optical disc drive.