The invention provides a body-mounted flat plane antenna for an inflatable satellite, belonging to the technical field of antennas. The body-mounted flat plane antenna comprises a reflection plane, an antenna module, a support ring and a support tube, wherein the reflection plane is fixed in a ring of the support ring, the antenna module is fixed at the lower side of the reflection plane, and the support tube is fixed at the upper side of the reflection plane. The invention solves the problems that the antenna caliber is difficult to enlarge due to the installation mode that the antenna is used as an accessory outside the satellite, and the precision and strength of signal transceiving of the whole satellite are greatly reduced due to the reduction of structural vibration base frequency. Compared with the traditional installation mode that the antenna is used as the accessory of the satellite, the body-mounted flat plane antenna is beneficial to enlarging of the effective caliber of the antenna and is also beneficial to improving of the whole structural rigidity and vibration base frequency of the satellite and greatly improving of the whole dynamics property of the satellite and the precision and strength of signal transceiving of the satellite.