Abstract: The friction loss of a FAW（First Automobile Work） production engine was reduced according to tribology structural optimization design and the diamond-like carbon (DLC) film. Based on the friction strip-down test and the performance test, the effect of main parameters of crank-connecting rod mechanism and valve train on engine friction loss was investigated, the effect of engine friction loss on the fuel consumption was investigated. The test results show that tribology structural optimization design and the diamond-like carbon (DLC) film can decrease mechanical friction loss of engine.mechanical friction loss of engine is decreased 17.1%, the low friction loss can improve engine performance. The fuel consumption is decreased 2.5%，providing a new working direction to energy saving and emission reduction.

Key words: power machinery and engineering, low friction, optimization design, diamond-like carbon film