An experiment of a single particle movement in vertical spiral rectangular duct has investigated with the aim to study the rotational Coriolis force based on kinetic model of single granular. The results indicate that: the dominant forces upon the particle are the centrifugal force, rotational Coriolis force, effectual gravity and drag force. There is exponential relation between λ and ζ, where λ stand for the ratio of tangential velocity of particle and water velocity, ζ stand for the ratio of rotational the Coriolis force and the centrifugal force. The probability of rotational Coriolis force and centrifugal force in the same order of magnitude is three-quarter. Therefore, the rotational Coriolis force should not be ignored on force analysis of a particle in small-scale rotational flow.