Financial institutions have raised loan quota, declined interest rates, and loosened conditions to increase the market share. However, this leads to a high risk of bad debt expense. The company we study is a leader for the Taiwan leasing industry, and automobile loan is its important business. The key of loan performance lies in the management of overdue repayment, so developing risk assessment model and reducing loan risk are important issues for the case company and even the whole leasing industry. This study invited experts to identify the main factors affecting risk assessment, and because the risk assessment of automobile loans is a grey system problem, the grey relational analysis forms the basis for developing the evaluation model. The specificity is the proportion of people who test bad debt among all those who actually do have bad debt. This means that the prediction model with high specificity is more useful for the company we study. Compared with other data mining techniques, since the results show that the proposed model has higher accuracy and specificity, it not only shows the superiority of the proposed model for risk assessment, but completely satisfies the practical requirements for the leasing industry. The proposed model has the benefit of simplifying the current review process by effectively reviewing car loan. By reducing the risk of bad debts, it can help the company we study to achieve the goal of sustainable development.