Abstract: For existing two-dimensional non-equilateral transform with scrambling effect poor and obvious texture feature, it is difficult to satisfy high security image information protection, so an improved two-dimensional non-equilateral Arnold transform is proposed and applied in scrambling pixel positions and encrypting pixel values to protect image information security. This method firstly makes good use of the constructing thought of classical invertible discrete standard map in hyperbolic dynamical systems, and embeds the nonlinear expressions of output results of one congruence equation for classical two-dimensional non-equilateral discrete Arnold transform into input item of the other congruence equation for two-dimensional non-equilateral discrete Arnold transform. Then a new good nonlinear transform with preserving area and period characteristics is constructed on the basis of two-dimensional non-equilateral discrete Arnold transform to improve the scrambling effect and reduce the image texture features. In the end, the original image can be restored from the scrambled and encrypted image by its periodic properties or inversed transform. Some experimental results show that the proposed nonlinear transform is effective, and can quickly obtain better scrambling quality and weaker texture features than the existing discrete two-dimensional non-equilateral discrete Arnold transform, meanwhile it has more practical value than the standard non-equilateral Arnold transform in view of security.