Generation adjustment is one of the frequently used measures to guarantee the safety of the power grid, however, it may encounter difficulties during practical dispatching since the adjusting ability is restricted by various aspects. The issue of generator output limitations (i.e. power congestion) caused by the capacity constraints of transmission channels is discussed. Such constraints are fit into the generation scheduling optimization under certain power grid operation mode, with power transmission maximization of the critical channels and the minimization of generator output adjustments as the objectives. Then the optimization model is supplemented with the statement of the possible special cases which may lead to the failure of searching the limitations. Following with the introduction of medium and long term maintenance plan, the updated optimization model is created and solved to obtain the adapted generation dispatching solution. The example of a provincial power grid verifies the effectiveness of the proposed method, indicated that it can improve the security and economic benefit effectively, relieve the man-power during the calculation, and eliminate the potential faults in manual intervention.