����First,the paper analyze the feature of down pressure in the overarm style structure,and figuring out it adoptsthe simple lever principle,which is used in the first generation CMP tool IPEC372M,and suit for 0.8��m technology node in the IC field.. Meanwhile the author indicates its disadvantage. Second,to introduce the bridge structure,adding the shaft sleeve and lever's chains which can make sure the spindle vertically to the platen. The kind of improved lever is very useful for the down pressure; Third,to study the tower structure,the patent belong to CETC 45,and it adopts the floated hanging flame,can achieve the real vertical down pressure to the platen. The tower structure has the pressure stably and very small force sensitively. Then,to analyze the carrousel structure of the AMAT's tool,and giving the structure's feature,it can apply the Membrane pressure instead of down pressure and back pressure, which realize the very excellent uniformity of the wafer. At last, pointing out the down pressure structure should has high reactive sensitively and less movement's parts.