Abstract: Study of the effect of the different ratio of hydrogen on cycle-by-cycle variations base on a methanol-hydrogen engine during 1 200 r/min and 1 800 r/min, the research results show that adding hydrogen cannot improve the combustion obvious and ratio of 6% hydrogen is better than 3% when the excess air coefficient lower than 1.4;while it can improve the combustion obvious and the higher ratio the better when the excess air coefficient exceed 1.4;while it cannot restrain the cycle-by-cycle variation when the excess air coefficient large than 2.0.