Quality of service(QoS) is a critical research issue in optimizing service composition execution path. Unfortunately, the currently existing methods ignore the hidden competition pressure between service providers which can push them to dynamically change their initial QoS values in that the initial optimal execution path can be changed. To address this isssue, an iteratively bargaining-based constraint correction strategy is proposed. With this method, an initial execution path for a service composition is firstly built by using the local optimization policy. Based on this path, the global QoS aggregating and checking models are used to determine all occurred QoS constraint violations. For all violations, the proposed bargaining strategy can be recursively used to correct such violations. Finally, an optimized path can be rebuilt to meet the overall end-to-end QoS requirements expressed by a user.