In this paper,the components of fatty acid from five kinds of animal oil,vegetable oil,swill oil and their refined oil were analyzed.The swill oil was detected by using the index of unsaturated fatty acid(U/S)、the contain of short chain fat acid、tridecoic acid、heptadecylic acid and odd carbon fatty acid as the endogenous substance of the swill oil.The result shows that the common edible oil could be distinguished from swill oil comparing by those three testing indexes.This method were effectively and quickly to reduce the misjudgments.