Cross-border transportation and multimodal transport have brought a more complex risk environment to the already high-risk transportation of dangerous goods. To effectively evaluate the risk of cross-border multimodal transportation of dangerous goods, based on the 4M factors (variables) of “human, machine, management and environment”, the two factors of “transshipment” and “international relations” in cross-border multimodal transportation are considered, and the six factors are taken as the attributes in the decision-making problem. Based on the randomness and fuzziness of the index factors, the cloud model is used to realize the mutual conversion between qualitative concepts and quantitative data, and the risk of cross-border multimodal transportation of dangerous goods is comprehensively evaluated and verified by the example. The simulation results show that the risk factors that have a greater impact on the safety of cross-border multimodal transport of dangerous goods include the clarity of safety rules, the degree of operational norms, meteorological environment, international politics and economy, and corresponding measures should be taken to prevent them. At the same time, it is verified that the proposed quantitative method can comprehensively analyze the accident factors.