Plasma surface modifications were performed on the aromatic copolyester liquid crystalline polymer surface to improve adhesivity to the polyimide matrix. Oxygen or ammonia plasma treatment on the liquid crystal polymer was fairly stable for one month, which was continuously confirmed by variation of contact angle. Peel strength test was employed to determine adhesivity between LCP and polyimide, and sessile drop contact angle was measured to study the surface properties of the plasma treated liquid crystal polymers. The surface morphologies of the plasma treated liquid crystal polymers were investigated as well. A mixture of 95% ammonia and 5% hydrogen plasma treatment on the liquid crystal polymer provided greatly improved adhesivity to polyimide.