A new 2D photonic crystal microcavity is proposed based on the localized modulation and the model match technique. Structure of the new PC cavity is characterized in that several scatters are introduced into the edges of the L3 microcavities. The local field modulation method is applied in the new PC microcavity to optimize the cavity structure, and the quality factor Q and transmission T can be both improved after modulation. During the modulation process, Q and T of the new PC cavity represent an identical variation trend. The Q and T of the optimized PC cavity, with the simulation parameters confined in our work, reach to 240000 and 0.68 respectively.