Faced with the rapidly increasing Web services, it becomes a challenging issue for users to effectively and accurately discover and reuse services. Existing service discovery approaches are mainly developed for services with WSDL documents, while only a few attention is being paid to services described in natural language,especially to the RESTful services. Towards this issue, we introduce a Weighted service goal model(WSGM) by measuring the weights of service goals extracted from the textual descriptions of services. Based on the WSGM, a novel service discovery approach called Service discovery based on WSGM(WSGM-SD) is proposed. Experiments on Programmable Web, a public Web service repository, demonstrate the effectiveness of the proposed approach. Faced with the rapidly increasing Web services, it becomes a challenging issue for users to effectively and accurately discover and reuse services. Existing service discovery approaches are primarily developed for services with WSDL documents, while only a few attention is being paid to services described in natural language, especially to the RESTful services. Towards this issue, we introduce a Weighted service goal model (WSGM) by measuring the weights of service goals extracted from the textual descriptions of services. Based on the WSGM, a novel service discovery approach called Service discovery based on WSGM (WSGM-SD) is proposed. Experiments on Programmable Web, a public Web service repository, demonstrate the effectiveness of the proposed approach.