In this paper,the effects of artificial reef on the vertical 2-dimensional steady flow fields with free surface were quantitatively discussed with numerical methods.In view of the current velocity and the water depth investigated in the artificial reef area at Shengsi,the value U_(in) and the depth H could be taken as 0.7 m/s and 20 m respectively.The influencing range and the strength of the upwelling field intensify with the increase of the reef height,and the range of the eddy behind reef has the similar features to the range of the upwelling strength.The average production and marginal production of upwelling field and eddy field reaches at the appropriate 0.1 ratio of the reef height to the water depth,after this,weakening with the increase of reef height.