The invention discloses a test method for measuring maximum dry density of soil and stone mixture of a road subgrade. The test method comprises the following steps of loading samples into a test die by two times, fixing onto a vibration compaction test instrument, and performing vibration compaction for two times, wherein the vibration compaction time is 50s each time, the parameter setting of the compaction test instrument is as follows: the vibration frequency is 25Hz, the excitation vibration force is 5.5kN, the nominal vibration amplitude is 1.4mm, the loading mass is 110+/-2kg, the unloading mass is 170+/-2kg, the eccentric block included angle is 0 degree, and the pressure of the static surface is 109kPa; testing the water content of each sample, and calculating the dry density of each sample; repeating the compaction test for five times, and drawing the dry density-water content relationship curve, wherein the transverse coordinate is the water content, and the longitudinal coordinate is the dry density; the dry density corresponding to the curve peak is the maximum dry density roudmax, and the corresponding water content is optimum water content omega0. The test method has the advantages that the operation is simple and convenient, the results are reliable, the variance is small, and the destroy to the raw materials is small.