The solid super acidic SO42-/ SnO2-kaolin was prepared by tin compounds and kaolin assisted by ultrasonic microwave drying method,it has a higher surface area and is used in the synthesis of food essence butyl propionate.The influence factors on conversion rate of n-butyl propionate were discussed,such as acid and butyl alcohol molar ratio,catalyst dosage,reaction time,type and amount of entrainer.The optimal reaction conditions on synthesis of butyl propionate were: the mole ratio of alcohol to acid is 2∶ 1,the dosage of catalyst 3% of the total reaction materials,reaction temperature 114 ~ 116 ℃,entrainer n-butyl alcohol,and reaction time 4 h.In this condition the esterification rate was up to 97.02%,much higher than the majority catalysis mentioned in the literature,the esterification rate still reached to 86.58% even when the catalyst was reused for third times,the purity of the product was 96.68% by GCMS.