Metasurface composed of sub wavelength metastructures have been the focus of research on plane optical lens in recent years,while plane metalens composed of metasurfaces has significant advantages in phase regulation,polarization control,holographic imaging,and stealth with negative refractive index. In view of the advantages of miniaturization,lightweight and easy integration of planar metalens,and the transmission based phase regulation principle is more suitable for the application of the near infrared band,and there is no special requirement for the incident light polarization state. In this paper,a silicon based metalens for the near infrared band is designed and optimized using the finite difference time domain method (FDTD).The designed metalens has a focal length of 15μm,a diameter of 20μm,anumerical aperture (NA) of 0.56,and a focusing efficiency of 68.3%,which is suitable for all incident polarizations and has excellent focusing performance within the target wavelength range of 700 nm. The results of this paper provide new ideas for the thinning and flattening near infrared metalens,which are expected to optimize the design of infrared detector lens and improve the efficiency of infrared detection.