The invention discloses a generator output sensitivity calculation method based on heuristic power flow calculation. According to the method, all PV nodes are converted into PQ nodes, the output of a researched generator set is independently and appropriately increased or reduced, the power flow of two state sections are then calculated, the difference value between the results of the two power flow sections is solved with regards to a concerned response quantity, and thus, the sensitivity coefficient of the active or reactive output of a certain generator to the power flow, the line loss, the node voltage of other circuits in a power grid can be calculated. By the method, the problems of complicated formula derivation, large calculation amount, easiness in error and heavy programming and solution working load in the conventional sensitivity coefficient calculation method are solved.