The wavefront curvature sensor comprising a phase defocus grating is designed and fabricated. The influence of zero-order diffraction is prohibited, and the high diffractive efficiency of 49% for the ±1 diffraction orders is verified experimentally. Wavefront deformation is introduced by a phase plate. The initial wavefront measurement experiment is carried out. The Green function algorithm is used for wavefront reconstruction. The reconstructed wavefront is compared with the measurement result of the Veeco interferometer. It is verified that the measurement of the self-designed curvature sensor is correct, the error percent of peak-valley value (PV) is 10%, and the error percent of root mean square (RMS) is 2%.