The analysis of energy helps to balance the imperceptibility and robustness of digital watermarking. Currently,the digital watermarking embedding energy is often determined by repeat testing. Firstly, this paper introduces the watermarking model which is based on the similarity of vectors, and then it quantificationally analyzes the impact of embedding strength and the secret key on the Peak Signal to Noise Ratio(PSNR)and watermarking correct extraction rate. Finally,simulation experiments show that with th...