The invention discloses a method for using order-different fractional-order system to design a sliding mode interference observer, and the concrete steps of the method comprises: obtaining relevant data by an excitation system; off-line identifying the order-different fractional-order model of the system; and according to the order-different fractional order of the system, designing a sliding mode interference observer for observing the disturbance at present online. The invention also discloses a product corresponding to the application of the method. The invention also discloses a method of applying the corresponding product to control the order-different fractional-order system. Compared with the traditional anti-disturbance method, the method of the invention uses the order-different fractional-order system model to design the sliding mode interference observer, which improves the accuracy of the disturbance observation and can realize the convergence in finite time to ensure the real-time performance of the observed results. In the case of strong interference, the robustness and stability of the order-different fractional-order system are enhanced. In addition, the method proposed by the invention is also applicable to an order-identical fractional-order system.