In order to solve the problems of the nuclear accident emergency drill, such as invisible radiation field, potential radiation risk, and high labor costs, therefore, an adaptive ray-casting 3D nuclear radiation field visualization method based on feature importance was developed in this study. The nuclear accident emergency disposal drill training simulation system was developed based on the Unity3D simulation engine. The 3D visualization of a nuclear radiation field with millions of grids was realized using ShaderLab programming. Multi-job personnel collaborative operation exercise simulation was realized based on the finite state machine. The system frame rate was approximately 60 frames, which meets real-time interaction requirements. Considering an out-of-control radioactive source accident as a case, the operation modes and emergency disposal processes of the nuclear accident emergency drill could be rebuilt by the system. The proposed solution of the simulation system could be applied to ensure personnel radiation safety, enrich training methods, and reduce training costs.