Abstract: The present disclosure provides a method for constructing a correlation model between relative bioavailability and bioaccessibility of cadmium in earthworm, belonging to the technical field of cadmium detection in earthworms. The method includes the following steps: determination of relative bioavailability of cadmium in earthworms, determination of bioaccessibility of cadmium in the earthworm based on an in vitro physiologically-based extraction test (PBET) method, and construction of a correlation model between the relative bioavailability and the bioaccessibility of cadmium in the earthworm. The method enables to directly put the bioaccessibility obtained by the in vitro method into a regression equation to obtain the bioavailability of cadmium in subsequent studies.