In the middle of the night, the excavator may encounter thieves stealing diesel. If some operators fail to lock the fuel tank after shutdown, it will increase the possibility of diesel theft. Most of the diesel stolen from excavators is pumped out through the fuel filler. The diesel tank can be quickly drained by preparing a common oil pipe. If the thief brings his own oil pump, it will be faster. The preventive method is to weld an iron cylinder with holes in the fuel filler, so that the fuel pipe cannot be inserted into the fuel tank. This will prevent thieves from stealing diesel easily.