Concurrent Multiple Negotiation (CMN) mechanism is necessary for agents to achieve agreements in multiple negotiations, and it has become a very important research topic in multi-agent systems in recent years. However, in the open and dynamic negotiation environment, negotiations may be dynamically and concurrently initialized or terminated during the process of other existing negotiations. Therefore, how to process dynamic CMN becomes a serious challenge in agent negotiation research. The motivation of this paper is to propose an adaptive mechanism for handling dynamic CMN by considering the possible changes of concurrent negotiations. First, a formal mechanism for modeling and representing dynamic CMN is presented. Then, a novel Colored Petri Net-based CMN protocol for processing CMN with unexpected negotiation changes is presented. We also demonstrate the performance and procedure of the proposed approach in handling the dynamism of negotiations in CMN, and the experimental results show that the proposed approach can effectively handle unexpected changes in the CMN dynamically, and successfully lead the CMN to agreements.