Abstract: Production of low calorie functional oil from soybean oil and propionic acid by enzymatic method in a solvent-free system was studied in this paper. It was found that immobilized 1-3 directional lipase enzyme LipozymeRM IM was better than Li-pozyme TL IM. The optimum reaction conditions for preparing of low-calorie functional oil was determined based on the principle of Box-Behnken design:temperature of 64.4℃, time of 8.8h, enzyme dosage of 8.4%, substrates/acid ratio of 3.3 ∶1 (mol/mol) , under the best conditions, propionic acid insertion rate was 14.85%.