For the real-time wavefront reconstruction method with the eigenfunctions of Laplacian in adaptive optics based on grating wavefront curvature sensor, three basic parameters including the selected light spot size and the position deviation on photoelectric detector, and the influence of the number of eigenfunctions modes on the precision of wavefront reconstruction are analyzed. The results show that the selected light spot size on the photoelectric detector has an obvious effect on the wavefront reconstruction accuracy, which can be obtained by the ring energy ratio. Because of other diffraction orders light on photoelectric detector, the position deviations of the light spot induce not only the wavefront tilt error but also other wavefront errors. The mode coupling due to the limited resolution can significantly affect the accuracy of the wavefront reconstruction when using too many modes, and the optimal mode number can be estimated via the correlation coefficient between modes.