Abstract: A new method of image watermarking in wavelet domain optimized by Firefly Algorithm is proposed to solve the problem that it is difficult to balance imperceptibility and robustness in watermarking.Firstly, the two layer Haar discrete wavelet transform (DWT) is applied on original host image, then singular value decomposition (SVD) is applied to the obtained second-level approximation subgraph LL₂, vertical detail subgraph LH₂ and horizontal detail subgraph HL₂, which are taken as the watermark embedding position.Then, the watermarking image is processed by Arnold transform and one layer Haar DWT.The SVD is applied to the obtained approximation subgraph LL₁, vertical detail subgraph LH₁ and horizontal detail subgraph HL₁, which are taken as the information to be embedded.Finally, the optimal intensity factor of watermarking embedding is obtained by using Firefly Algorithm (FA).The experimental results show that the proposed algorithm can well balance the imperceptibility and robustness of the image watermarking.