In recent, a general trend is observed towards more customized products and shorter product life cycles in manufacturing companies. In these companies, customers often wish to influence the product they order and to get a variant of product that meets their requirements. This environment is called as a customer-oriented manufacturing companies. This paper presents a procedure of product specification management for customer-oriented manufacturing companies by using product specification framework. This framework is founded on the product specification based product structure which is made of model, specification, function, and part. Also, a product specification management system(PSMS) is implemented by using the proposed product specification framework and is a core system in product data integration system. To illustrate an utilization of the proposed framework and procedure, a case of a ship engine product is applied. As a result, PSMS reduces delivery time and improves customer relationships. Moreover, the case shows that PSMS can be used as a tool for improving inter-department coordination within a company during product life cycle.