The invention discloses a method for preparing butyl sorbate, which comprises the step of reacting sorbic acid with n-butyl acetate to obtain the butyl sorbate under the condition of toluene serving as a water-carrying agent and p-toluenesulfonic acid serving as a catalyst and negative pressure of between 37.3 and 61.3kpa. In the method, the water-carrying agent toluene and water are used to formazeotrope; the water generated by the reaction is carried away at esterification temperature in time, so that the esterification reaction speed is greatly increased and the esterification reaction time is shortened. The water is removed under negative pressure to reduce the polymerization phenomenon, a large amount of the butyl sorbate is prepared, so that the cost is reduced and the yield is improved; and the experiment proves that the yield of the butyl sorbate under the negative pressure is greatly improved.