The invention relates to a method for identifying waste oil by using Caenorhabditis elegans dormancy as a biological marker, and relates to a waste oil identifying method. The method of the invention solves the problems of low sensitivity, poor accuracy, complex operation and high cost existed in the current waste oil identification method. The method comprises the following steps: 1, uniformly mixing NaCl, agar powder, peptone, a CaCl2 aqueous solution, a MgSO4 aqueous solution, a phosphate buffer and distilled water to obtain a nutrient solution, then sterilizing, and drying to obtain a medium; and 2) coating escherichia coli OP50 bacterial liquid in a prepared medium in the step 1), culturing for certain time, and culturing Caenorhabditis elegans larva for 46 hours. The method has the following advantages that 1, effective identification of high refining waste oil with low specific component trace can be realized; and 2, the operation is convenient, the cost is low, the method is easy to train and grasp. The method of the invention is mainly used for identifying the waste oil.