Elastic resource provisioning is one of the key techniques for cloud computing, as it can make resources to be organized and provided on demand, resolve the contradiction between resource utilization and user satisfaction, and ensure higher service level agreement. Considering the deficiency of the present cloud resource managements, we propose an innovative elastic resource provisioning approach with a loosely coupled and scalable architecture for cloud based on docker. The elastic resource provisioning method combines both dynamic virtual clustering techniques and economic benefit analysis theories. The results show that our approach can meet the resource supply requirements of elastic cloud with excellent scalability, great agility, strong robustness and high resource utilization.