The movement of small particles in a vortex flow is simulated by lattice Boltzmann method. The vortex flow is produced by a flow in a cave, and the trajectory, velocity and anglular velocity of the particles are evalnated with the hydrodynamic force calculated by the momentum-exchange and stress-integration, respectively. At last, multiple particles with different radii moving in a vortex flow are also simulated with the hydrodynamic force calculated by stress-integration.