To study the water migration mechanism of granite residual soil （GRS） during evaporation and dehydration， a series of nuclear magnetic resonance tests and microscopic tests were conducted on Shenzhen GRS. In this study， the formation reasons for the dual-pore structure of GRS were analyzed. We investigated the water distribution under different degrees of saturation and proposed the mechanism of water migration in GRS. The results show that the micropore structure of GRS is formed by the cementation between iron oxide and kaolin layers； the dual-pore structure is constituted by the micropore and macropore structure which is not easily disturbed； the micropore structure and macropore structure are interconnected at high saturation， and the hydraulic connection is interrupted at low saturation； water evaporates synchronously between the dual pore structures and the supply from the macropore structure to the micropore structure decreases with the evaporation. This research can provide the theoretical basis for water migration in complex soil structures.