Gas-liquid-solid three-phase flow is common in various fields, making it crucial to accurately and efficiently describe its dynamic behaviors. To better perform the gas-liquid-solid three-phase simulations, a coupling code based on GPU named as CoSim-FVDEM is developed, which combines the finite volume method (FVM) and the discrete element method (DEM). This code encompasses unresolved, resolved and resolved-unresolved coupling methods, making it suitable for three-phase flow simulations involving solid particles of various sizes. A series of cases are conducted to validate the accuracy of the developed coupling algorithm, including complex dam breach flow, water entry test of a single sphere and multi-sphere within rotating roller. Finally, a gas-liquid-solid three-phase flow numerical experiment is performed, which involves the bi-disperse granular systems in a rotating roller. Base on the numerical results, the dynamic behaviors of the three-phase flow are analyzed and the computational efficiency is evaluated. The results indicate that the developed coupling code can better be used for the dynamic analysis of large-scale gas-liquid-solid three-phase flow.