The invention aims at solving the problem that the accuracy of the existing inertial navigation system is affected by plumb line deviation to be reduced, discloses a plumb line deviation compensationmethod based on a gravitational field model and belongs to the technical field of inertial navigation. By adopting the plumb line deviation compensation method including the steps of normal gravity vector calibration and calculation, plumb line deviation calculation based on a gravitational field model, compensated gravity vector calculation according to plumb line deviations, initial alignment, navigation calculation and the like, the influence of plumb line deviations on an inertial navigation system is compensated, the inertial navigation positioning accuracy is improved, the steps of the method are simple and easy to achieve, the influence of plumb line deviations on inertial navigation can be reduced without additional hardness costs, and the accuracy of the inertial navigation systemis improved.