The variable relationship between the threshold of the extrapolation and its correspondent Peak of the Signal-to-Noise Ratio(PSNR) in the Wavelet Bi-linear Interpolation Algorithm is deeply analyzed. The Maximal PSNR Wavelet Bi-linear Interpolation Iterative Algorithm is proposed. This algorithm can automatically search the optimal extrapolation threshold to improve the resolution of the optical remote sensing image without damaging its original information,which makes the detail information of the processed image more favorable to be observed and analyzed. The experiment results show that the PSNR of the image reconstructed by this algorithm is 5.5 dB and 2.5 dB higher than that of those reconstructed by the Bi-linear Interpolation and the Wavelet Scale-Function Interpolation respectively,and its entropy is 1.3 times of its original image. It is an effect algorithm to improve the spatial resolution and entropy of the Optical Remote Sensing Image.