This study surveys the influence of the floor underpricing regulated by TSA to ROI of foreign companies which are primary listed on Taiwan capital market. The result we find is that the ROI of these most companies ever listed in emerging stock market is apparently lower than the companies not listed in emerging market. We suggest that the reasonable underpricing should be evaluated by related profession and come up with international capital market trend. Additionally, we also suggest that the execution of book building should be carried out with auction to allocate the subscription following the orderly auction price, and the rest the only book building adapted so that it can effectively diminish the underpricing fraud.