A reputation mechanism is critical for a distributed service environment. A customer can select the optimal services to compose a value-added composite service based on services' reputation. However, a composite service obtains only one score (or feedback) after every invocation. In order to compute the reputation of every component service, it is necessary for the composite service to distribute this score to its component services. How to achieve a fair distribution is a challenging issue, as each component service may perform differently in contributing to the success or failure of the composite service. Although several efforts have been made for this problem, they do not consider the structure information of composition, which makes the distribution unfair. Therefore, in this paper, we propose a fair score distribution framework which combines the structure-related importance of component services and their runtime performance. Experimental results show that our approach can achieve a more reasonable and fair score distribution than existing methods.