The invention provides a low-radar-scattering-cross-section microstrip antenna comprising: a dielectric substrate, a radiation patch, an artificial magnetic conductor surface, a metal floor, and a defect ground. The artificial magnetic conductor surface constitutes a checkerboard structure by a first artificial magnetic conductor unit array and a second artificial magnetic conductor unit array. The defect ground includes a square annular groove obtained by etching the metal floor. The two different artificial magnetic conductor units of the microstrip antenna can satisfy a phase difference of180 degrees +/-30 degrees in a wide frequency band, thereby realizing a purpose of reducing the wideband radar scattering cross section of the antenna. Compared with an original antenna, the microstrip antenna is significantly increased in antenna gain. Due to the floor-etched defect ground structure, the reflection curve of the artificial magnetic conductor units in the vicinity of the antenna radiation patch shifts to the low frequency so as to reduce the radar cross section in a lower frequency band without changing the size of the artificial magnetic conductor unit and provide a new idea for miniaturization design.