The invention discloses a monopulse radar non-blind area distance measurement method and system with a protection channel. The system comprises a slot array main antenna, a protection antenna, a tuner, a circulator, an intermediate-frequency receiver, a signal processor, a secondary power source and a transmitter. The system is a monopulse system; the slot array main antenna periodically transmitshigh-frequency pulse signals, and the protection antenna receives target echo signals in real time; transmitting and receiving are carried out correspondingly, so that transmitting and receiving canbe separate; when no distance measurement blind areas exist, sum channel, azimuth difference channel and pitch difference channel data are formed by echoes received by the slot array main antenna, thesum channel, azimuth difference channel and pitch difference channel data are adopted to perform target distance measurement; when a distance measurement blind area exists, the slot array main antenna is used as a transmitting antenna, and the protection antenna receives echo data, and therefore, protection channel data can be formed; the protection antenna carries out real-time receiving to realize non-blind area distance observation, and meter-scale distance measurement requirements can be met; and finally, distance measurement is performed through a pulse method, and distance measurement precision is improved through pulse compression, so that radar distance measurement precision requirements can be met.