The relative diffraction performance of soft Xray phase condenser zone plate and amplitude zone plate is obtained by measuring the first order diffraction intensity. The experimental setup is simple and relatively easy to adjust. The size of the pinhole is selected to obtain sufficient signalto-noise ratio. The thickness of the polyimide substrate is normalized. The first order diffraction intensity of three Ni and three Ge zone plates is compared with that of an Au zone plate. The experimental average first order efficiencies of the Ni and Ge zone plate are 1.60 and 1.26 times that of the Au amplitude zone plate at 3.2 nm, which are close to the theoretical results: 1.77 and 1.34. The measurement result indicates that the phase zone plates fabricated has high accuracy.