A public-key asymmetric robust watermarking algorithm based on signal with special correlation characteristic is proposed in this paper. This algorithm is designed to permit pubic watermark detection while preventing the watermark from being removed without the private keys. A signal, which is pseudorandom sequence with special auto-correlation characteristic, is used as watermark, and the signal's characteristic is the foundation of this algorithm. Therefore we first construct the method of generating the pseudorandom sequence and prove its auto-correlation characteristic. Then we describe the algorithm in detail. Experiment results show that the algorithm is valid and robust to common signal distortions and malicious attacks. Keywords Public-key; robust watermarking; pseudorandom sequence; auto-correlation.