The invention relates to a heat preservation protective device for a molten iron tank of a molten iron vehicle, and belongs to the technical field of iron and steel enterprise molten iron vehicle devices. The device is used for preserving the heat of transported molten iron. According to the technical scheme, a protective cover is composed of two relative semicircular cover bodies, the two semicircular cover bodies are in butt joint and are matched with the top surface and the outer periphery of an opening in the upper end of a molten iron tank, the upper ends of two supporting frames are connected with the two semicircular cover bodies of the protective cover correspondingly, the lower ends of the two supporting frames are connected to the front end and the rear end of the molten iron tank of a molten iron vehicle through vehicle body hinging seats, two hydraulic cylinders are arranged at the front end and the rear end of the molten iron vehicle, the lower ends of the hydraulic cylinders are connected with the vehicle body, the front ends of hydraulic push rods of the hydraulic cylinders are hinged to the middles of the supporting frames, and the hydraulic cylinders are connectedwith hydraulic pumps. The device has the beneficial effects that the excessive temperature drop of the molten iron in the molten iron tank of the molten iron vehicle can be avoided, the smooth proceeding of the subsequent steelmaking process is guaranteed, the production efficiency is improved, the molten iron in the molten iron tank can be protected from being influenced by external factors, andthe safety of the device and personnel is guaranteed.