To measure the transmission wavefront of a large-aperture aspheric lens, we propose a method by using a computer-generated hologram (CGH) as a phase compensation element. The transmission wavefront of a large-aperture aspheric lens is typically tested by a sphere interferometer. To conduct a null test, phase compensation is required to compensate for high-order aberrations (HOAs). However, validating the accuracy of conventional refractive-phase compensation elements is difficult, and they therefore generate unreliable measurement results. An alternative type of phase compensation employs a CGH, which is a diffraction element that can also be used to conduct a null test. To conduct a null test for the transmission wavefront of a large-aperture aspheric lens, we design and manufacture a CGH. A contrast test is implemented with two different phase compensation elements, which results in two measured data those are very similar to one another, between which the peak valley (PV) difference is 0.034λ (λ is the wavelength of the detect light), and the root mean square (RMS) difference is 0.006λ. Therefore, the null-test method using a CGH proposed in this study displays a high degree of accuracy.