In this paper, a new design of microstrippatch antenna based on grid structure in the Ka-band is proposed which can realize optical and microwave coaxial detection.Both the patch and ground boardis designed into dense grids, at the same time, using the transparent glass as the medium plate. As is shownin the simulation results, in this concerned wave band, compared with ordinary microstrip patch antenna, furthermore, the antenna designedachieve a good antenna radiation characteristics, while realize the barrier-free transmission of light, make the light transmission rate over 90% which achieve the goal of optical and microwave coaxial detection.