It is important to save energy and improve system performance by applying the technology of variable frequency speed regulation in fans. This paper proposes the efficiency optimization control strategies for single fan operation, parallel and serial operation respectively based on operational situations. The regulating rate of speed is obtained by analytical mathematical equation in single fan operation. But for parallel and serial operation, the regulating rate can be obtained only through solving optimization models by nonlinear programming methods. The models are practical as computation and precision are taken into account comprehensively. The paper presents the experimental results and application at last.