The work aims to improve the design of the existing forearm myoelectric prosthesis products to solve the problems of high abandonment rate and low usability, and to enhance the utilization rate of forearm prostheses for the upper limb disabled and defective people. Fault Diagnostic Tree Analysis (FTA) was applied to find the underlying root causes of the existing problems, the TRIZ theory was introduced to define the root causes using terminology and transform them into TRIZ general engineering parameters, which were described and analyzed to form one group of physical contradictions and three groups of technical contradictions. The corresponding inventive principles for problem solving were found by querying the Archie Schuller contradiction matrix for technical contradictions, and specific solutions for physical contradictions were generated by separating the principles to guide the overall design innovation to form the optimal solution. Specific solutions were generated to guide the overall design innovation to form the optimal solution. Under the guidance of the user's specific needs positioning for design improvement, a systematic and effective design solution which was more consistent with the needs of the forearm amputee population was obtained and three-dimensional modeling product design was conducted. By combining the two theories, the specific using needs are effectively located to form solutions rapidly and provide a reference for innovative design of similar prosthesis products.