Abstract: Four methods for mechanism reduction including reaction path analysis,path flux analysis（PFA）,isomer integration and sensitivity analysis（SA） were coupled to reduce a detailed reaction mechanism（5 027 species and 19 988 reactions） with five major biodiesel methyl esters in the real biodiesel as fuel components,and a reduced mechanism containing 183 species and 748 reactions was constructed. The reduced mechanism was comprehensively validated by comparing the ignition delay,instantaneous temperature,and combustion state based on perfect stirred reactor（PSR） with the original mechanism,and with the experimental data of ignition delay based on shock tube and the experimental data of molar fraction of important species in jet stirred reactor（JSR）. The results show that the comprehensive method for mechanism reduction adopted can more completely retain the key reaction characteristics of the original mechanism,and the reduced mechanism can better predict the combustion and emission characteristics of biodiesel.