Carboxyethiosuccinic acid (CETSA) was selected as anion and four kinds of novel ionic liquids were synthesized by one-step method. Their structures were characterized by 1H NMR、13C NMR、TG、MS and FTIR respectively, confirming the successful synthesis of ionic liquid catalysts. β-mercaptopropionic acid was synthesized by Michael addition reaction from acrylic acid and hydrogen sulfide (H2S). The catalytic effect of ionic liquid was investigated. The optimal process conditions are: tetrahydrofuran (THF) of 35 g, acrylic acid of 2.16 g, sufficient hydrogen sulfide in situ to replace the traditional gas cylinder, the ionic liquid of 3mmol, the reaction temperature was 90 ℃, and the reaction time was 4.5 h in the hydrothermal synthesis reaction reactor. At this time, the results showed that 1,5-diazabicyclo[4.3.0]-5-nonene carboxyethyl thioglycoate ([DBNH]CETSA) showed the best catalytic effect, and the conversion rate of acrylic acid was 100% and the selectivity of product was 90.57%. [DBNH]CETSA still has high activityafter repeated use for 7 times, and the conversion rate of acrylic acid still reached 98.97%, indicating that the ionic liquid catalyst was relatively stable in the reaction.