For the first time, a highly isolated common aperture low-profile microstrip antenna is designed and realized to work in four frequency bands—L/S/C/X, simultaneously. The overall structure is made by stacking microstrip antennas of four bands from bottom to top according to the order of frequency from low to high, using coaxial probes through the low-frequency radiation patch to form an over-hole to feed the high-frequency antenna and using the lower-frequency antenna as the ground of the higher-frequency one in turn to improve the antenna index and performance. Among them, each radiation patch of L/S/C band adopts the way of adding branches around a rectangular radiation patch, which is conducive to impedance adjustment. The X band radiation patch is placed at the top layer, and by slotting the rectangular patch, the radiation blocking to other bands is avoided. By adopting the method of neutralizing line decoupling and orthogonally feeding, the gain in the four bands is finally realized as 6.85 dBi, 7.48 dBi, 6.13 dBi, and 6.62 dBi respectively. The isolation between each port is greater than 30 dB. The antenna size is 85 mm×85 mm×9.07 mm. By means of the physical processing , the test results and simulation ones match well, which verifies the validity and reliability of the design.