The invention relates to a multilayer micro-strip flat-plate array antenna with symmetric beams, which consists of a radiation layer, a feeder layer and a reflection plate, wherein radiation patches are symmetrically distributed on an inner surface of the radiation layer, and the radiation patch array is totaled in 18 units of 3*6; the feeder layer is arranged between the radiation layer and the reflection plate, a distance between every two adjacent layers is a quarter wavelength, a grounding surface of the feeder layer is provided with 18 H-shaped coupled gaps in a form of 3*6, a micro-strip feeder line is arranged on the feeder surface of the feeder layer, on a micro-strip feeder-line network, energy is allocated by a first-level power distributor to a second-level power distributor and is opposite to a phase position, finally the energy is allocated to each radiation unit through a serial impedance matching circuit, the reflection plate is a metal plate and forms an inner surface of an antenna shell, the radiation layer also has a function of an antenna cover, and the entire antenna is completely arranged inside a closed shell except a connector.