This paper presents a model-based systems engineering (MBSE) approach to develop an upper limb spasticity part-task trainer for therapy training and clinical education. We adopt a value-driven design proposed by the American Institute of Aeronautics and Astronautics (AIAA) with the combination of specification technique CONSENS™ proposed by Heinz Nixdorf Institute as a framework to guide the team to optimize the perceived system value and the development process. As early as during the conceptual design phase, the specified system models take into considerations the Voice of Customer, the Voice of Business and the Voice of Technology to meet customer expectations, ensure cost effectiveness and enabling new functionality. Following such an approach, clinicians, therapists and engineers work together in order to develop an upper limb disorder part-task trainer which requires knowledge of mechanics, electric/electronics, control technology, software engineering, biology and human anatomy. As an education tool, the part-task trainer can multiply the frequency of novice therapy training at clinical training centres, medical schools and hospitals.