Existing evaluation and testing methods are difficult to apply to the wavefront aberration test at different elevation angles for a photoelectric telescope with 3—4 m aperture. Therefore, this paper presents a Wavefront Error(WFE) test method by subaperture wavefront slope discrete sampling and then reconstructing the full aperture wavefront aberration. On the basis of the co-simulation by mathematical analysis and optical simulation, it studies the relationship between wavefront reconstruct accuracy and sub-aperture scanning motioned tilt error, sub-aperture scanning position tilt error, image point coordinate measuring error and wavefront reconstruction algorithm uncertainty. Collaborative simulation results show that the relative error(ΔPV) of iterative algorithm is about -0.002 8λ (λ=632.8 nm), and the relative error(ΔPV) of pattern algorithm is -0.002 7λ. When the sub-aperture tilt error is less than 0.2″, the wavefront reconstruction error(ΔPV) is about 0.02λ. When the sub-sampling aperture position error is less than 0.2 mm, the wavefront reconstruction error(PV) introduced is less than 0.04 nm. And when position error of imaging point is less than 5 μm, the wavefront reconstruction error (ΔPV) introduced is less than 0.03λ.The results demonstrate that the pattern algorithm has a higher error margin, and the convergence is better when the measurement errors are considered. Moreover, it suggests that it should take the angle monitoring and error compensation mechanisms into account and the angle measuring accuracy of the sub-aperture tilt monitoring system should be better than 0.2″when an actual measuring equipment is established.