Anonymity technologies have gained more and more attention for communication privacy. In general, users obtain anonymity at a certain cost in an anonymous communication system, which uses rerouting to increase the system’s robustness. However, a long rerouting path incurs large overhead and decreases the quality of service (QoS). In this paper, we propose the Scalar Anonymity System (SAS) in order to provide a tradeoff between anonymity and cost for different users with different requirements. In SAS, by selecting the level of anonymity, a user obtains the corresponding anonymity and QoS and also sustains the corresponding load of traffic rerouting for other users. Our theoretical analysis and simulation experiments verify the effectiveness of SAS.