The sensitivity of infrared optical imaging systems is closely related to the transmittance of optical windows, and Ge windows are commonly used windows in infrared optical systems. Fabrication of subwavelength structures on Ge windows can enhance the antireflection performance so as to improve the optical transmittance, and the Ge windows are usually convex shaped to get a larger field angle. However, based on current methods, it is difficult and complicated to fabricate subwavelength structures on curved windows. To solve this problem, this study presented an efficient and high-quality way to fabricate subwavelength antireflection structures on the convex Ge window based on soft ultraviolet nanoimprint lithography (soft UV-NIL). The parameters of the subwavelength antireflection structures were optimized based on the finite-difference time-domain method first. The subwavelength structures were fabricated on the convex Ge window by soft UV-NIL. Test result shows that the average single-side transmittance of the convex Ge window is raised from 65.81% to 78.68% in the region of 3.55-5.55 μm, and specifically, from 65.85% to 83.13% at the wavelength of 4.4 μm. As a result, the broadband antireflection performance in mid-infrared is realized.