Real-time safety correction of overload line flow is of great significance for improving the safe operation level of power systems. Existing sensitivity-based correction algorithms rarely consider the correction cost of the generator and cannot guarantee the economics of the correction scheme. Therefore, a real-time correction method for overload lines based on quasi-steady-state sensitivity and correction cost minimization is proposed. First, the shortage of the power generation transfer distribution factor and the advantages of quasi-steady-state sensitivity are analyzed. Then, the comprehensive sensitivity is used to reflect the comprehensive influence of node injection power on the power of all overloaded lines, and then the most effective control generator set for eliminating line overload is screened. Finally, an optimization model is set up with the least correction economic cost and the least number of generators involved in the correction as the objective function, and the model is solved using a mixed integer linear optimization method. The obtained correction scheme can ensure that the generator runs at a lower cost under the condition of eliminating line overload, and the number of generators involved in the correction is small, and the practicability is stronger. The IEEE 39 and IEEE 118-node systems are used to simulate the calculations, demonstrating the fast and effective algorithm. This work is supported by National Natural Science Foundation of China (No. 51277134).