In this paper, a microstrip-based parasitic element decoupling structure is used to design a high-isolation patch antenna array consisting of a C-shaped microstrip line and two short pins. The structure is symmetrical at the center, and a bunch of identical microstrip line structures are placed symmetrically on both sides of the patches. The frequency is within the bandwidth of 3.27 to 3.37 GHz, and the return loss of the antenna is less than -10 dB. After adding a microstrip line decoupling structure between the two patch antennas, the isolation between the antennas is increased from the original 22 dB to more than 33 dB. Moreover, the added decoupling structure can effectively improve the antenna's radiation pattern.