In China, business groups usually choose the same auditor to be in charge of multiple listed firms within the group. Based on this starting point, this paper makes use of non-financial IPO firms from 2003-2012 to test whether choosing the same auditor in the group as the IPO auditor affects IPO underpricing and post-IPO underperformance. This paper revealed that choosing the same accounting firm to audit for all companies within a group cannot play an information role in the primary market and it will obviously increase the underpricing with the post-IPO operating performance declining later. After comparing and analysis among accounting firms of different sizes, the result shows that small accounting firms can better interpret this function.