One of the most important operation in Internet, is the discovery of web services, because of the increasing use of this technology in the last years, as well as, Cloud computing technology is becoming the new way to conceive applications in the network, due to the capacity of treatment and storage offer by the Cloud based systems. In this work we propose, new web services discovery architecture based agents in open cloud computing federation. More accurately, we propose a new algorithm of comparison between the request of the client and the description of the Web services, this algorithm aim to select and rank the discovered web services to give more precision to the web services that the system return to the client. The proposed system is composed of two areas of Cloud. The first deals with Key words based research and the second supports the filtering of the found web services based on a new matching algorithm for web services selection. The results show the efficacy of the proposed architecture in the optimization of the quality of service (QoS) (the response time in our case) due to, on the one hand, our v our virtualization policy, and the use of mobile agents to maximize the exploitation of the Cloud computing resources.