Phase measuring deflectometry (PMD) is a technique for measuring optical three-dimensional profiles of specular and mirror-like objects.However,when measuring the transparent object,the reflection light from its bottom surface mixes with that created by top surface.This phenomenon produces the superimposed fringe patterns which leads to decrease the measurement accuracy.An effective method based on the principle of muti-frequency and phase-shifting is proposed to solve this problem.By analyzing the relationship between the phase errors and fringe frequencies,and utilizing the characteristics of the modulation curves and introducing an auxiliary function,we can find a special frequency at which the unwrapped continuous phase is equal to the phase of the top surface in theory.Due to the complicacy of a lens,the continuous phase order calculated by temporal phase-unwrapping algorithm frequency-by-frequency may be error.So the order correction method is proposed to solve this matter.And then the screen coordination of the top surface can be obtained by the correction algorithm.The top surface shape can be reconstructed subsequently.Experimental results of measurement of a spectacle lens demonstrate that the proposed method can successfully untangle the phase of the front surface from superimposed reflections.