The long-run underperformance of the initial public offerings is one of the three hot issues in IPO research area,until 2000,the scholars in China began to research it,hence,the related theory is far from absent,therefore,many theories need to be completed. The article studied the long-run performance of 174 shares issued in Small and Medium-sized Board from the day after the first trading day to three years.It found that the shares show underperformance since the first month after its going to public,which will continue to the second year.But the shares showed strong performance compared with the Shenzhen A-share Composite Index.