The uniform and high brightness illumination light is the key for testing the projection objective lens in deep ultraviolet region with nanometer accuracy by using the method of Shack-Hartmann wavefront sensor. The intensity contrast of the wavefront diffracted by the random arrangement pinhole array is optimized by using finitedifference time domain method and the theory of partial coherence. The wavefront diffracted by the pinhole array with random arrangement is smoother compared with that with periodic arrangement. Analyzing the wavefront diffracted by the single pinhole shows that the larger the pinhole diameter is, the bigger the intensity contrast of the wavefront will be. The intensity contrast of the wavefront diffracted by double pinholes reaches to maximum value when their separation is 74 nm. The calculation and analysis show that, to obtain the wavefront whose intensity contrast meets the requirement of nanometer accuracy wavefront error metrology, the diameters of the pinholes in pinhole array with random arrangement should be 170 nm and their separations should not be less than 306 nm. In this case, there are 428 pinholes in the pinhole array, and the intensity contrast of the wavefront diffracted by them is 11.70.