Aiming at the problems of difficult processing， low precision and poor effect of fabricating geometric phase elements in crystal materials， a femtosecond laser-induced nano-grating technology was proposed to fabricate the internal geometric phase diffraction elements. The femtosecond laser near-threshold processing method effectively improves the processing accuracy and the fabricating accuracy is 340 nm. By adjusting the polarization of the scanning laser， the direction of the induced nano-grating can be accurately controlled， leading to the change of the slow axis direction of the crystalline birefringence. Based on this method， the geometric phase Fresnel zone plate in sapphire has been fabricated. The device has a good morphology with no cracks and excellent optical performance， which can be used for focusing in high-temperature environments.