The Karhunen-Loeve (K-L) expansion is used to extract coherent structures from a leading-edge separation bubble with local forcing. A leading-edge separation bubble is simulated using the discrete vortex method, where a time-dependent source forcing is perturbed near the separation point. Based on the wealth of numerical data, the K-L procedure is applied in a range of the forcing amplitude (A(0) = 0, 0.5, 1.0 and 1.5) and forcing frequency (0 less than or equal to f(F)H/U-infinity less than or equal to 0.3). Application of K-L procedure reveals that the eigenstructures are changed noticeably by local forcings. In an effort to investigate the mechanism of decreasing reattachment length (x(R)), dynamic behaviors of the expansion coefficients and contributions of the eigenfunctions are scrutinized. As the forcing amplitude increases, large-scale vortex structures are formed near the separation point. Furthermore, the flow becomes more organized, which results in the reduction of x(R). Two distinctive regimes are classified: the regime of decreasing x(R) and the regime of Increasing x(R). The K-L global entropy indicates that x(R) is closely linked to the organization of the flow structure.