Abstract: In road engineering, fine particles invade reinforced gravel base and cause pollution, resulting in deterioration of mechanical properties of reinforced soil interface. Considering the two factors of fine particle pollution amount and normal stress, this paper adopts self-developed visual pullout test equipment, digital photographic measurement technology and MEMS wireless sensor to carry out the pullout test of geogrid and road base gravel packing under different fine particle content, and explores the changing law of pullout force, particle displacement, coarse particle rotation angle and geogrid strain during the test. The degradation mechanism of fine particle pollution on reinforced soil interface was revealed. The test results show that with the increase of fine particle pollution degree, the peak pull-out force of geogrid decreases gradually, especially when the pollution degree is 30%, the interface deterioration factor reaches 20%; Fine particle pollution not only increases the displacement of coarse particles, but also reduces the scope of indirect influence zone, thus weakening the reinforcement effect of geogrid; The particle disturbance degree of the upper interface of the grid is more obvious than that of the lower interface. The number of interface folding angles on the X axis, which indicates the stability of coarse particle skeleton, is reduced from 8 when the pollution degree is 0% to 1 when the pollution degree is 40%, and the deformation degree of the geogrid also decreases gradually with the increase of the pollution degree.