The fourth party logistics services are able to combine excellent logistics services through largescale integration of resources, and provide the best logistics services scheme for the user through combination of technology, warehousing, transportation service, thus realizing the logistics service with high efficiency, low cost and realtime operation. However, how to dynamically construct reliable composite logistics service that can satisfy users’ quality requirements is the critical issue for the fourth party logistics service provider to solve. To address this issue, the paper proposes a dynamic composition method of contextaware logistics Web service. Firstly, this method decomposes the global QoS constraints into local QoS constraints based on the improved genetic algorithm, and transforms the global optimization problem into a local optimal service selection problem. Secondly, during the execution of the service process, the best logistic Web service that is available and can satisfy the local QoS constraints is selected. Finally, the effectiveness and feasibility of the method are validated by experiments.