Establishing an effective evaluation mode for design alternatives is critical to develop a successful and competitive product in the intense marketplace. In this study, the personal digital assistant (PDA) was used as a targeted product to be developed and evaluated. Several highly feasible design alternatives were created based on the analyzed concepts of design elements and desired product images. The evaluation model is base on the algorithms of grey relational analysis. The evaluation criteria were collected and screened from the customer's requirements. The priorities of criteria were also assessed using the analytic hierarchy process and thus the designers can better understanding the importance degrees of customer's requirements. According to the analyzed data for PDA, the design components including functionalities and form features were identified. The layout and various form types of design components and product image were also defined to conduct product development. Five design alternatives were measured using rating scales of linguistic variables. After aggregation operation for the judgment of decision makers, the decision matrix can be derived for the grey relational analysis. Based upon the analyzed grey relational degrees of each design alternative associated an ideal solution, the ranking order for design alternatives can be obtained. The results indicate the proposed evaluation model can assist designers to conduct effective design decision in the product development process.