A novel watermarking sharing system having the ability of sharing gray-level secret images with multi-user is proposed. Multiple-based number system is used to split the secret into n meaningless shares, each share is embedded into respective cover image with controlled distortion and to be assigned to each user afterwards. The architecture of the proposed watermarking system is an open issue, which means the system is easy to be implemented according to the purposes and concerns of the users. The main feature of the proposed system is sharing a secret of gray-level image among multi-users; another application of such system is ownership verification. To reveal the secret, the necessary amount of shares has to be presented. That is, the secret can be recovered even if some shares were lost. Simulation results show that the recovered secret has robustness against a wide range of imaging processing operations.