Abstract: Web Services technology has been developing rapidly in the recent years, but the adopt of rate is very low all along because of the problem of QoS in Web Services. So, this paper analyzed problem of QoS of Web Services in the project of Dynamic Composition of Web Services, presented a computation model of QoS and a computing method of QoS Optimization, the scheme supports dynamic binding of Web Services, automatic and semiautomatic executions and optimal choice of Web Services based on QoS and so on. Lastly, the prototype and implementation were introduced.

Key words: Web services,Dynamic composition,QoS model