According to the selecting properties of ionic liquids,1-(4- sulfonic acid) butyl -3- methyl imidazole hydrogen sulfate and other fifteen kinds of ionic liquids were synthesized by the two step synthestic method. Using the sixteen ionic liquid’s instead of concentrated sulfuric acid as catalysts for the synthesis of methyl propionate, the researches showed that reaction speed of 1-( 4- sulfonic acid ) butyl-3- methyl imidazole hydrogen sulfate saltionic liquids was the fastest, it could make the concentration of methyl propionate reach 66.12% within 20 min,the concentrations of methyl propionate was the highest,and reach 74.67%,so its catalytic effect was the best in the final reaction system.