Service composition involves combining many existing services to solve a complex task in the service-oriented environment. Due to the progress in modern smart devices, mobile devices can now act as service providers. The mobility of mobile service providers and the dynamism of the mobile environment are unique features. As a result, there are two issues with service composition in mobile environments: (1) how to use the mobility of devices as an non-functional Quality of Service (QoS) criterion, and (2) how to deal with the dynamism of the mobile environment to realize the optimal service composition. In order to deal with above issues, we proposed a QoS-aware service composition model for service composition in mobile environments considering the feature of mobility in the mobile environment. Moreover, we proposed an adaptive approach called k-neighbor. The main idea of k-neighbor approach is to decompose the composite service into smaller elementary composite services then to set up a solution plan for those elementary composite services based on the available provider set. The evaluation shows that the way of decomposing a composite service adapts to different dynamism of the environment.