The invention provides an automatic prefabricated part splitting method based on BIM and a computing device. The method comprises the steps that an overall BIM of a building project is designed, splitting parameters are built, and splitting rules for the number, the classification, the output information content and the project amount of a prefabricated part are made according to the preset splitting parameters; the overall BIM is classified according to the splitting parameters, and a building type is determined, so that mistakes are prevented from being made in the subsequent splitting process; the overall BIM is split into refined models step by step through two-time splitting, and in the subsequent part verification process, only part of models need to be verified, and the overall model does not need to be verified, so that the work efficiency is improved; the overall BIM is decomposed into a set of various parts and split into the minimum units meeting the production manufacturingand transporting requirements, and the part shapes are subjected to restoration verification, so that splitting errors are avoided; a production drawing of the part shapes is directly output, and theaim of one-key splitting design of the prefabricated part is achieved with the combination of the splitting requirements of the prefabricated part. Therefore, the accuracy and the efficiency for designing the drawing of the prefabricated part based on the BIM are improved.