An extended ptychographical iterative engine (ePIE)-based method is proposed to accurately measure the transmitting wave-front of an imaging lens. The laser beam exiting the imaging lens is illuminated on a diffraction object fixed on a two-dimensional scanning stage, and the diffraction pattern is formed on the subsequent detector. The scanning stage transversely scans and records the diffraction pattern formed by the diffraction object at each position. The complex amplitude of the laser field incident on the diffraction object is faithfully reconstructed from the recorded diffraction pattern using the proposed ePIE algorithm, and the wave-front of the transmitted laser on the rear surface of the lens is retrieved using the Fresnel equations. Additionally, the wave-front illuminated on the lens can be reconstructed by repeating the above mentioned procedures after the lens is removed. Then, the transmitting wave-front of the lens is obtained by subtracting the illuminated wave-front from the exiting wave-front. The proposed method has several advantages including high accuracy, simple structure, and low cost.