The utility model discloses an oil bottom shell of a diesel engine, which comprises a main body of the oil bottom shell, wherein the main body of the oil bottom shell is provided with a side wall and a bottom wall. The upper part of the main body of the oil bottom shell has an opening connected with an engine body, and the side wall of the main body of the oil bottom shell is provided with an oil passage. An outlet of the oil passage is communicated with a lubricating oil passage arranged on an engine seat, and the bottom wall of the main body of the oil bottom shell is provided with an oil pool. The side wall of the oil pool upwards extends and is provided with an upper opening, and the upper opening of the oil pool is provided with a filtering net. An inlet of the oil passage, which is arranged on the side wall of the main body of the oil bottom shell, is communicated with the oil pool. Compared with the prior art, the oil bottom shell of a diesel engine has the advantages that an oil pipe is omitted, the part number is reduced, the space size of a diesel engine is decreased, the installation is convenient and the operational reliability of an oil supply system is improved.