Entrainment of the topsoil at Tiaozini beach is vulnerable to water flow，and it leads to the collapse of embankment toe，thus protection measure shall be taken.Appropriate protection measures are associated with the threshold velocity.The threshold velocities of the fine silty sand sampled from the topsoil at Tiaozini beach under different water depths are tested by indoor experiments，and compared with those calculated by several widely used calculation formula，including Zhang Ruijin，Dou Guoren，Tang Cunben，et al.Based on the results of the experiments，suitable formula for the threshold velocity of fine silty sand of topsoil at Tiaozini beach are proposed.