The main drawback of the traditional quantization index modulation (QIM) watermarking is its extreme sensitivity to scaling attack. Due to scaling have a little effect on Discrete Cosine Transform (DCT) coefficients, this paper proposed a novel robust image watermarking algorithm based on QIM in the DCT domain. In the presented scheme, the medium and low frequency DCT coefficients of host signal are divided into two parts, then the watermark bits are embedded by quantizing ratio of l_p-norm of the two parts. Experimental results confirm the superiority of the proposed algorithm against common types attacks in comparison with the recently proposed scheme.