The invention provides a method for controlling threshold-crossing of active power of wind power plant and power grid connecting line sections, and belongs to the technical field of operation and control of new energy access power systems. The method includes the steps that according to the deviation between an active power real-time value and an upper limit value of the wind power plant and power grid connecting line sections, a section set needing threshold-crossing correction is determined, in combination with the sensitivity of the active power of wind power plants to the active power of the wind power plant and power grid connecting line sections, wind power plant active power regulating capacity constraints and power grid safety constraints, a secondary planning model is constructed, and threshold-crossing of the sections are eliminated and fair dispatching of the wind power plants is taken into consideration. The method can be integrated into a wind power generation active power control main station system operating in a dispatching center, the system can take the most appropriate control policy in real time according to the wind power generation operation state and the power grid operation state, safety of the active power of the wind power plant and power grid connecting line sections is guaranteed, and fair dispatching of the wind power plants is taken into consideration.