The issue of reliable communication resulting from Agent moving is studied in the paper. Based on analyzing current solutions to the issue, a mechanism called Active Communication Mechanism (ACM) is proposed, which can provide reliable and efficient communication for mobile Agents. The detailed analysis regarding the reliability and efficiency of ACM is also presented. ACM can reliably and efficiently deliver the sender's message to receiver allowing the free migration of both them and guaranteeing the exactly-once semantics for message delivery. ACM can serve as the basis of high-level communication mechanisms such as Agent communication language.