The invention discloses a lower cylinder body of an automobile engine, comprising an installing surface of a back end flywheel shell, a left side surface, a right side surface, a combining surface of an upper cylinder body, a combining surface of an oil bottom shell and an installing surface of a front cover, wherein the installing surface of the front cover extends out of the front end of the lower cylinder body; a timing chain wheel is positioned in the extending position so that the installing surface of the front cover of the cylinder body and the front cover form one-dimension sealing inassembly process; and the combining surface of the oil bottom shell and the oil bottom shell form the one-dimension sealing in a whole engine state. The design of the lower cylinder body of the engine is completely suitable for die-casting process of high speed and high efficiency and meets the requirement of the quick development of automobile industry; the lower cylinder body solves the supply bottleneck of key parts and components, solves the problems (such as timing and phase position) of regulation, replacement and the like of the inner part of the engine and reduces the trouble of disassembling relative parts of the engine and potential risks such as leakage and the like.