The embodiment of the invention provides a stability analysis method and device for an airplane structure rectangular flat plate. The method comprises the steps that electronization is carried out on a curve chart of dual-pressure shearing and buckling related curves of the rectangular flat plate, and curve data is obtained, wherein the x-coordinates, the y-coordinates and values on the curves of the curve chart are marked as CurveRx, CurveRy and CurveRs in the curve data respectively; Rx, Ry and Rs are calculated according to the compression allowable stress sigma ccrx of the rectangular flat plate in the X direction, the compression allowable stress sigma ccry of the rectangular flat plate in the Y direction, the shearing allowable stress tau cr, the compression working stress sigma cx in the X direction, the compression working stress sigma cy in the Y direction and the shearing working stress tau; the CurveRx value, the CurveRy value and the CurveRs value meeting formula (I) are sought in the curve data based on a binary search algorithm; the safety margin MS=K-1 of the rectangular flat plate is calculated; the stability of the rectangular flat plate is analyzed according to the safety margin MS. By means of the method and device, the worked out safety margin is high in scientificity and reliability, and therefore the stability analysis result of the airplane structure rectangular flat plate is more reasonable and reliable.