Multi-focus lens is applied widely as an important optical element, but it has stringent requirements for manufac-turing and assembling micro-lens array which is used for multi-focusing in traditional methods. So tiny error is inevitable, which may affect the usage performance. Therefore, it is necessary to design a new type of multi-focus optical device. Metasurface is a kind of artificial surface which consists of many subwavelength antenna units different from traditional optical element. Metasurface utilizes the anomalous refraction properties that subwave-length antenna units response to the electromagnetic wave to modulate wave front. Subwavelength scale antennas with different structural parameters are arranged according to certain rules, so it can realize flexible modulation to amplitude and phase of electromagnetic wave. Metasurface has been widely used in the designing of various new optical components in recent years. Compared to the conventional multi-focus lens, metasurface is used to design multi-focus lens with its unique advantages. In finished works, when designing the multi-focus lens based on metasurface, the phase retrieval algorithm is used to obtain the phase distribution of lens commonly, and multiple iterations are performed between metasurface and the focusing surface. However, this method for phase calcula-tion is of great computation load, and sometimes it is easy to fall into local optima. Meanwhile, metasurface-based flat-lens array also be proposed. It consists a number of regularly arranged lenslets to achieve multi-focusing function, but the array structure is not favorable to be integrated. Computer-generate holography (CHG) method to design multi-focus lens based on metasurface has been proposed in far-infrared region. This method is simple, straightforward, accurate, and easily implemented and realized. Firstly, 8 C-shaped resonant rings aimed at central frequency 28 THz(wavelength 10.71 μm) were designed, which was able to modulate the phase of transmitted cross-polarized wave from 0 to 2π and amplitude transmittance remains constant, that can be used in the design of multi-focus lens. Secondly, the anomalous refraction functions of this set of resonators were verified by full-wave simulation when linearly polarized light waves were irradiated normally. It can be seen that the wavefronts of the deflected waves with cross-polarization are well deflected, further demonstrating the broadband property of the resonators. Finally, the four spot light source in focusing plane were set as certain distance away from the plane where metasurface located. The phase distribution of multi-focus lens at metasurface was calculated by the method of complex amplitude superposition. Then, according to arranged C-shaped resonators based on obtained phase distribution, a square metasurface-based lens was got, and the structure was simulated as a integer by CST Microwave Stdio. Simulation results show a good multi-focus performance at 28 THz while the focal length is 108 μm, as certain broadband response characteristics in 27.6 TH~28.5 THz.