The invention provides a detection method of a road surface bituminous mixture separation degree. The evaluation method comprises the following steps of: firstly, respectively determining a grading lower limit, a grading upper limit and a grading middle value according to the grading type of a road surface bituminous mixture; preparing a coarse bituminous mixture according to the grading lower limit, preparing a middle bituminous mixture according to the grading middle value, and preparing a thin bituminous mixture according to the grading upper limit; secondly, mixing the coarse bituminous mixture, the middle bituminous mixture and the thin bituminous mixture together to form track test specimens, and establishing correlationship between the penetration time and void ratio of different grading bituminous mixtures through a permeability test and a void ratio test; and thirdly, evaluating the separation degree of the road surface bituminous mixture according to the correlationship. The evaluation method provided by the invention has the advantages that the operation is simple and easy, the detection sensitivity is high, an evaluation result is exact and reliable, and a separation condition after pavement of the road surface bituminous mixture is rapidly and accurately evaluated.