The invention discloses an assembly protecting device for nuclear fuel assembly conveying containers. The assembly protecting device structurally comprises a protecting plate and rib plates. The protecting plate is connected to a container assembly bearing component through protecting plate supports and supporting plates, and the rib plates are fixedly connected to the protecting plate. The protecting plate supports include a top support and side supports and are used for connecting the supporting plates with the assembly bearing component. The supporting plates include top supporting plates and side supporting plates and are used for connecting the protecting plate with the supports. The assembly protecting device has the advantages of convenience in processing and operation and anti-impact performance, and solves the protecting problem of impact load perpendicular to the axial direction of a nuclear fuel assembly during conveying of the assembly. The assembly protecting device is applicable to the nuclear fuel assembly conveying containers and the like.