The invention discloses a multimode multiband radio-frequency onboard micro-micro cellular communication system based on software defined radio, which comprises a receiving module, a local oscillator module, a transmitting module and a control module. The radio-frequency micro-micro cellular communication system can support multiple working bands and working modes: 800-1000 MHz (GMSK (Gaussian Minimum Shift Keying)/CDMA (Code Division Multiple Access) 1X), 2.412-2.472 GHz, and 5.0-5.8 GHz (QPSK (Quadrature Phase Shift Keying)/QAM (Quadrature Amplitude Modulation) 16/OFDM (Orthogonal FrequencyDivision Multiplexing)-QAM 64). In particular environments, such as aircraft flight and the like, the radio-frequency micro-micro cellular communication system can support different radio network services: GSM (Global System for Mobile Communications) (935-960 MHz/890-915 MHz), CDMA (824-849 MHz/869-894 MHz), 802.11b/g (WLAN (Wireless Local Area Network) 2.412-2.472 GHz) and 802.11a (WLAN 5.0-5.8GHz) communication systems. The channel bandwidth varies as the operation mode varies. The maximum bandwidth can reach 20 MHz, the maximum radio-frequency output power is 20 dBm, and the noise factorof the receiving machine is less than 9 dB.