An experimental platform based on a microfocus X-ray grating interferometer is established to support the wavefront control of high-performance light sources and the development of advanced experimental technologies, and facilitate laboratory-level surface shape measurement at a working wavelength. X-ray grating interferometry is a highly sensitive wavefront sensing technique and can be used to quantitatively measure the X-ray wavefront distortion. Furthermore, the phase of the fringes and the wavefront radius of curvature distribution are reconstructed by phase stepping and Fourier analysis, so as to calculate the wavefront angle and mirror slope error distribution. The measurement results obtained by Fourier analysis are in good agreement with the long trace profiler, with the root mean square of their difference less than 200 nrad. The proposed technique can be used for online wavefront feedback and control in X-ray active optics, error detection of reflection, refraction and diffraction devices, and quality evaluation of X-ray beams of large scientific devices.