Abstract: The reasons why the operating performances of the public companies in Liaoning Province all felloff after IPO are analyzed with their panel data in view of their earnings, solvency, business operations and developmental capability. The nonparametric MNR method is used for stability test to ensure the reliability of the following conclusions by the analysis made, and a cross-section regression model is developed to discuss empirically the main influencing factors on the operating performances of those public companies. The results show clearly that their performance falloff were mainly due to the factors as follows: the difference in trades, ownership structure and the years they went to public, especially 2001 and 2002. It is revealed that the growth rate of net profit of industrially public companies were obviously lower than other trades. However, the state-owned stock equity was proved beneficial to improving the operating performance of public companies. Some suggestions are given on empirical basis.