Abstract: Based on property of electrical ball valve and combined with pipeline characteristic of oil unloading system in tankfarm。valve shut—off scheme to control water hammer of the system is researched with characteristic method and comparison and analysis between theoretical result and measured data are carried out.Results show that under the given condition, continuous three—step valve closure to control surge is most effective, that is, the first step should pass quickly, and the second and third step should pass slowly. And it is most effective to control surge when total time of the last two steps closure is 4 to 5 times than that of the first step, and closure angle of the first step is 2.7 to 3.5 times than that of the last two steps. Under the same operating condition, parabola control to close valve during the third step is better than that of linear control.