Abstarct: Due to the increasing development of communications in today's world, the need for optimal control of communications in administrative different environments, multimedia, physical, digital and security becomes more and more clear.Copyright protection of data against copying and forgery of documents is very important.For this reason, it should be used from mechanisms to control unauthorized copying. Watermarking method has a set of characteristics that should be considered.The most important of these characteristics are transparency, robustness, security and the watermark capacity.These characteristics are transparency, robustness, security and the watermark capacity, thatthe most important of them are transparency and robustness. The purpose of transparency, is invisibility embedded datain the image.The purpose of transparency is invisibility embedded datain the image and the robustness is to resist watermarked image against unintentional and intentionalattacks and the various image processing.Also, the number of bits that is hidden in an image indicates the watermarking capacity. There is an inverse relationship between capacity and robustness in watermarking system. In this thesis, a watermarking method is proposed baxsed on three-level discrete wavelet transform for digital gray level images.In the proposed method to increasing the capacity of watermarking system, the improved gray scale quantization technique is used.Then, the Arnold transform is applied. This transform distributes the changes of pixels after the attacks in the whole imagethat will increase transparency.The proposed method improved transparency and robustness characteristics and also, it increases the watermarking capacity.The simulation results show that the proposed method in addition to have acceptable resistance and transparency, it has more capacity in compare to reference method.