The invention relates to the technical field of medical accelerators, and discloses a medical accelerator. The medical accelerator includes an acceleration pipe, a beam pipeline, a beam scraper, a corrugated pipe and a beam needle, and the beam pipeline, the beam scraper, the corrugated pipe and the beam needle are connected in sequence and share a central axis and communicate to form a straight channel for transmission of an electron beam in the straight channel; and an inner pore diameter of the beam scraper is smaller than an inner pore diameter of the beam channel. The invention also discloses a dose monitoring system. The dose monitoring system includes a resistance, a voltmeter, a conductor and a data processing system, the beam scraper, the resistance and the ground are sequentiallyconnected through the conductor, and the voltmeter is used to test a voltage value at both ends of the resistance; and the data processing system processes the voltage value to obtain a dose of the electron beam. The invention also discloses a dose monitoring method. A current is generated through part of the electron beam, the voltage at both ends of the resistance is simultaneously tested, andthe dose rate of the electron beam is obtained by testing the voltage value, so that the treatment process is not affected, and online monitoring of the dose of the electron beam can be realized.