This paper presents an adaptive iterative denoising algorithm based on noise estimation for terahertz images. First, the noise standard deviation of the real experimental image is obtained by using the noise level estimation method, and then the noise image is denoised by using quadtree based weighted double square non-local mean denoising method to improve the quality of the reconstructed image. Finally, the noise estimation and denoising of the denoised image are carried out again, and the best denoising effect is obtained through repeated iterations. Experimental results show that the method can retain the details of the image, effectively removes the background noise caused by the imaging system, and has a good denoising effect on terahertz image.