Quality is defined as several terms of fitness for use, conformance to requirements or specification, and loss of social effect. And the quality can be classified into design, production and service quality according to its formation of product (or servece). To be satisfactory product, the product must be controlled to maintain the specified level of quality at the whole life cycle of R&D step through disposal step. And the wrong design is one of the great source of cost. Therefore, the quality assurance on the R&D step is very important. This paper suggests a general procedure for the R&D quality assurance and discusses the methods for the reliable design. And a telecommunication equipment is considered as an applied example. Finally, it is discussed some subjects on the R&D quality assurance as further researches.