The article studies the effects of density of soybean molasses,fermentation temperature,fermentation time,inoculation quantity,pH on the production of ethanol used soy molasses.through orthogonal test,the results showed that the optimum conditions were: molasses concentration 55g/L,fermentation temperature 32℃,fermentation time 72h,inoculation amount of 9%,pH value 5.0.Under the optimal conditions,the ethanol production yield was 7.3%vol.