The present invention relates to a manufacturing method for a mid-infrared lens, which includes the following steps: placing a lens in the path of a far-infrared radiation source, enabling the lens to receive the far infrared rays; immersing the lens in a hardening liquid, causing the hardening liquid to coat the lens, wherein the hardening liquid is an intermixture of silicone and isopropanol or an intermixture of silicone and methanol, and a far-infrared material or a far-infrared composite material is additionally added to the hardening liquid; placing the lens coated with the hardening liquid in a drying space to dry, causing the hardening liquid to dry and harden and form a hardened layer on the surface of the lens. The temperature of the drying space lies between 80 and 120° C., and the drying time lies between 1 and 10 hours.