Passive millimeter-wave images are heavily blurred due to the low-pass filter effect of antenna and the influence of noise. Aiming at the problem, an improved method of nonlinear extrapolation in frequency space was proposed and ap- plied to passive millimeter-wave image enhancement. This algorithm changes the form of nonlinear filter, and denoises the image by combining with the method of total variation minimization. Experimental results show that the new method can im- prove the quality of passive millimeter-wave image and reduce the noise more effectively compared with the original algorithm.