During the optical interference testing, the measurement accuracy of the tested surface is influenced by the system structure of interferometer, which will decrease the reliability of the measurement. To obtain high measurement precision, it is necessary to analyze the testing system and build the relationship between the measurement error and system structures. With the Fresnel diffraction approximation method, the influences of the collimated lens and standard lens surface errors on the transparence testing are analyzed in Fizeau interferometer. Through analyzing the propagation of the wavefront phase, we obtain the correlation between the wavefront error and system structure parameters, remove the empty system error, optimize the structure parameter, and build up the expression about the tolerance limit of the collimated lens. We draw the conclusion that when the aberration of the tested surface is 0.2λ, the measurement error can reach 0.02λ, and the aberration of the collimated lens 0.8λ will be enough.