Maintainability an important property of the product, which is mostly determined in the design stages. Maintainability design including many aspects, such as visibility, reachability, maintenance space, ergonomics and safety. The design effect of maintainability directly influences the maintenance activity during the service stage. Today, while designers can perform maintainability design with the help of computer-aided design (CAD) software, the complexity of maintainability design poses a significant challenge to designers in terms of time cost and knowledge requirements. This paper reports a case study on how to utilize virtual reality (VR) technology to help designers with design work. A workflow is established to instruct each specific implementation step of VR, from system level to component level. The entire design work can be divided into the simulation phase and the evaluation phase. For the aspects of the maintainability, corresponding evaluation criteria and methods are established. When the simulation is finished, the designer can analysis and evaluate the maintainability status with these criteria and methods. Following the established workflow, the integrate maintainability design work for several subsystems of a helicopter is conducted. The suspected design problems are classified into three levels according to their hazard ratings. The verification on the physical prototype proves that most suspected design defects do exist. The benefits and challenges of using VR to assist maintainability design are also discussed.