Wavelet tree based watermarking algorithms are generally using the wavelet coefficient energy difference for copyright protection and ownership verification. Since there are cryptanalysis based methods addressed for successfully attacking wavelet tree based watermarking algorithm of WTQ, it is the motivation in this research to devise a scheme to improve WTQ's robustness. Therefore, a chaotic system is adopted for WTQ to counteract the attacks in this paper. The digital image is first split into many blocks and the chaotic system is applied to scramble the image before the implementation of WTQ. The experimental results demonstrate the effectiveness of using chaotic system to enhance the security of WTQ, especially, to resist cryptanalysis attack. In addition, such mechanism also works for other wavelet tree based algorithms like WTGM and TED.