The order parameter of Duffing-Holms model is analyzed and found out. Existence conditions of Duffing-Holms model's periodic solutions are put forward, which indicates that we can control financial chaos in OGY method and nonlinear synchronous method. One periodic solution is set out before numerical simulation of OGY is done. The conclusion has demonstrated that, to control effectively chaos in Chinese financial market, the government must prepare fully and adjust slowly. Finally, the conclusion of numerical simulation of nonlinear synchronous controlling has demonstrated that the government can control stock markets of Shanghai and Shenzhen by indentifying one market as the driven system and the other as the controlled response system.