The invention relates to a method for automatic and classified collection of test waste oil under vacuum negative pressure. Test waste oil flows into an oil color detection device through an oil collection groove for detecting and distinguishing fresh oil or old oil; if the oil is fresh, the oil flows into a fresh oil sealing oil storage box through an oil separating pipe to be stored; if not, the oil flows into an old oil sealing oil storage box through the oil separating pipe to be stored; meanwhile, the vacuum degree inside the fresh oil sealing oil storage box and the vacuum degree inside the old oil sealing oil storage box are monitored in real time through a pressure transmitter; if the vacuum degree inside the fresh oil or old oil sealing oil storage box is lower than -0.05 Mpa, a vacuum pump is started for vacuumizing; the fresh oil and old oil sealing oil storage boxes are communicated with a fresh oil floating ball liquid indicator and an old oil floating ball liquid indicator respectively for monitoring the oil quantity of the fresh oil and old oil sealing oil storage boxes; if the oil quantity inside the current fresh oil or old oil sealing oil storage box reaches a specific threshold value, oil drainage is performed through an oil drainage pump. The method has the advantages that test waste oil is collected in an automatic and classified mode, the waste oil oxygenolysis speed is slowed down, and evaporation of volatile oil is reduced.