Because the surface of plastic products is often stained with organic substances such as fingerprints and oil stains, and inorganic substances such as dust attached by electrostatic action, these stains should be removed. The reasons for refining waste engine oil are introduced as follows. The principles and steps of the regeneration and refining method of waste engine oil are as follows: Reasons for refining waste engine oil: refining fuel oil from waste engine oil not only saves resources, but also protects the environment, so the recycling of waste engine oil has become a common cognition of society. Principle and steps of waste oil regeneration and refining method: the waste oil is cracked in a micro-negative pressure cracking furnace at room temperature with high operating safety factor, and the obtained oil product is light in color, low in viscosity and low in sulfur content. A catalyst can be added in the liquefied gas process, so that the obtained oil product has good appearance and can be sold, which saves the complicated procedures of acid and alkali and reduces the production cost.