In the process of barrierfree shield receiving, when shield cutting GFRP reinforced concrete retaining pile, the pile body may deform towards the empty side of foundation pit, and even cause the whole collapse. Therefore, the mechanism of cutting GFRP reinforced concrete retaining pile by shield needs to be studied. Based on PFC3D, the discrete element particle flow model of shield cutting pile is established, and the variation laws of cutting force and pile stress are obtained. The shield mechanism of barrierfree receiving and pile cutting is revealed: the first half of the cutin stroke is shearcompression failure, and the second half of the cutin stroke is shear failure. The thrust of shield should be controlled well during cutting piles to avoid the overall collapse of retaining piles.