The invention provides a coarse aggregate separation degree estimation index, a coarse aggregate separation test device and an asphalt mixture separation degree estimation method. The main point is as follows: 1) the weighted average of coarse aggregate grading deviation of each area of a material pile is used as the separation degree estimation index; 2) the test device comprises a support, wherein a funnel is fixed on the support and used for containing coarse aggregate mixed in proportion, the bottom of the funnel can be closed, and the coarse aggregate falls into a liftable receiving plate through the funnel; multiple concentric isolation barrels with different inner diameters are arranged and penetrate through the declining receiving plate, and the coarse aggregate enters each isolation barrel; 3) the device is used for the coarse aggregate separation test and calculating the coarse aggregate separation degree estimation index; 4) a separation degree index model equation is established through regression analysis; 5) the asphalt mixture separation degree is estimated by use of the model equation and design grading information. The technical principle is clear, the device is simple and convenient to produce, the test and calculation process is simple, and the estimation method is reliable.