The invention discloses an image super-resolution reconstruction method based on a back-propagation neural network. The contents of the method mainly include image input, preprocessing, image denoising, image-border maintaining and the back-propagation neural network. The method includes the steps that first, a synthetic aperture radar image is preprocessed, multiplicative noise of the image is converted into additive noise, an improved non-local mean value is adopted to conduct the denoising, and an exponentiation operation is adopted to restore the image; then, a kernel function is adopted to maintain clear borders of a reduced image; finally, through the treatment of the back-propagation neural network, a super-resolution reconstruction result is obtained. According to the method, a neural network model is adopted, and a large number of computing resources and a large amount of calculation time are saved; according to the improved non-local mean value method, a low-resolution image is reconstructed into a high-resolution image, speckle noise of the synthetic aperture radar image is denoised, and the combination of the modified non-local mean value method and the back-propagation neural network greatly improves the reconstruction effect.