The increasing use of Web services as well as the growing interest lent to Cloud computing technology and its capacity of calculation, storage and Cloud services, impose today that the traditional mechanisms of discovery must be re-examined. This specificity of discovery over the cloud led us to propose a new approach based on mobile agents dedicated to Web services discovery. More accurately, we propose a new algorithm of comparison between the request of the client and the description of the Web services. Our system is composed of two areas of Cloud. The first deals with Key words based research and second supports the filtering of the found web services. This discovery is performed by an algorithm based on the calculation of similarities between the request and the description of the web services.