The invention discloses a symbol timing synchronization method in MPSK signal demodulation, and belongs to the field of digital communication signal processing. The method is characterized in that timing synchronization is achieved by extracting symbol rate deviation and feeding back and controlling an interpolation position. The symbol rate deviation can be extracted by adopting a Gardner synchronization algorithm independent of carrier frequency deviation; according to the interpolation algorithm, an improved basis polynomial interpolation method is adopted, parameters of the filter can be optimized and solved at an output extreme point of the filter, and the method has more accurate synchronization precision compared with cubic interpolation filters, parabolic interpolation filters andother interpolation filters.