The invention relates to a control method and system for improving the passing efficiency of a narrowed road section. The control method comprises the steps: S1, the average speed, the flow and the traffic flow density, obtained at each sampling moment, of various types of vehicles in various lanes of various road sections are recorded; S2, a traffic flow prediction model is established on the basis of a Multi-Class CTM model and in combination with the number of vehicles for speed limiting and lane changing of different lanes, and a measured value serves as an initial condition for predictingfuture dynamic conditions of traffic by the prediction model; S3, based on the traffic flow prediction model, an objective function and constraint conditions of an optimization problem are established, and a finite time domain optimization problem is solved; and S4, the first element in the optimization problem solution sequence acts on the controlled object based on a rolling optimization framework of model prediction control, the next sampling moment is entered, and the steps are repeated until the whole sampling time period is completed. According to the scheme, the application speed and the traffic state change between different lanes within limited time after lane changing control are predicted, and the prediction precision is improved.