An iterative phase retrieval algorithm is put forward, which makes use of intensity distributions on the input plane and several fractional Fourier transform planes. The intensity distributions on the input plane and other two fractional Fourier transform planes with relatively high orders are utilized to retrieve the phase profile, then the phase detail is retrieved by using other two fractional Fourier transform planes with relatively low orders. Good retrieval performances are obtained for two-dimensional slowly varying phase distribution and random phase distribution. Finally, the influences of the measurement noise and the fractional order error to the stability of this algorithm are analyzed in one-dimensional case, respectively.