This paper first analyzes the definition and characteristic attributes of virtual currency transactions, secondly constructs the legal risk indicator evaluation system, then pre-processes the evaluation data and assigns the indicators, and then constructs the legal risk evaluation model using TOPSIS-grey correlation. Finally, the quantitative data analysis was carried out by analyzing the indicator weights and evaluating indicators. The results show that the overall score of the trading platform is 73.86, with the evaluation scores of the first-level indicators being 24.56, 11.35, 16.23, 15.42, and 6.30, respectively. This study fully illustrates that the use of TOPSIS-grey correlation analysis can provide data support and a decision-making basis for legal risk assessment and prevention and new directions for reforming and developing the legal risks of virtual currency trading.