Due to the nonlinear nature of height-phase relation, the traditional phase shifting shadow Moiré can only be fulfilled under certain approximations. Thus a systematic error source is introduced. Therefore, a general phase extraction algorithm with arbitrary phase step based on iterative self-tuning algorithm is proposed. In the proposed method, the estimation of phase shift is calibrated by the least squares fitting in spatial domain. Then, the accurate phase is obtained by an iterative process. Numerical experiments show that the proposed method can effectively minimize the nonuniform phase-shift error and can determinate the precise phase shifts during the process of demodulation. In the noisy case, the calibration error of the proposed is less than 3.4%. The experimental results prove the effectiveness of this technique. The proposed method improves measurable depth range.