The effect of scour and siltation on permeable frames is affected by the length-width ratio of permeable frames，the length of span and the length of frame.The control variable method is adopted to study the effect of the length-width and ratio of permeable frames on the flow reduction.The results show that when the overhead rate is constant，the deceleration rate decreases firstly and then increases with the aspect ratio，and the deceleration rate takes the maximum value when the aspect ratio is 16.The deceleration rate increases firstly and then decreases with the increase of the overhead rate，and when the overhead rate is 4.8，the frame deceleration effect is the best.The contour map of deceleration rate with overhead ratio and length width ratio is used to quantitatively describe its distribution law，and the influence of permeable frame ratio and ratio of length to width on flow deceleration rate of river channel is analyzed.