Despite the great momentum gained about the testing, analysis and verification of BPEL process, little attention has paid to the debugging issues, especially about the building of ad hoc debuggers. In this paper, we propose and implement RBDB (Reversible BPEL DeBugger), a specially made reversible debugger for BPEL process. RBDB is built on the abstract debugging APIs to fulfill itsfunctionality. A reversible concurrent debugging model and three strategies to handle different type of external web services are introduced later. Finally, a comprehensive analysis of experiment data are presented. Evaluation results demonstrate that RBDB can improve users' efficiency significantly and decrease the invoking times of external services substantially.