A system of electron irradiation, comprising an electron accelerator, an electron beam focusing device, wherein the electron accelerator is arranged for emitting and accelerating a beam of electrons, wherein the electron beam focusing device is located at a rear end of the electron accelerator and comprises a beam restraining rail and 2n+1 sets of magnetic poles (1-4, 5-8, 9-12) wherein the beam restraining rail forms a beam restraining channel through which the beam of electrons are to pass, wherein the 2n+1 sets of magnetic poles are installed on the beam restraining rail and are distributed at different locations of the beam restraining channel, wherein an nth set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a first direction, wherein an (n+1)th set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a second direction, wherein the second direction is perpendicular to the first direction, wherein the n is a positive integer, wherein the system further comprises an electron beam detecting device arranged for detecting the beam of electrons, wherein the electron beam detecting device comprises an electron collecting device, a shield room, a communicating box, and a controller, wherein the electron collecting device is located together with the electron accelerator inside the shield room, and is arranged for acquiring a first signal by detecting a strength of the beam of electrons radiated by the electron accelerator, wherein the communication box is located outside the shield room, wherein the controller is located outside the shield room, is connected to the communication box, and is arranged for controlling detection of the beam of the electrons; characterised in that the electron beam detecting device further comprises a sampling box, wherein the sampling box is located inside the shield room, is connected to the electron collecting device, and is arranged for receiving the first signal and converting the first signal into a second signal which is an optical signal that reflects a degree of uniformity of irradiation of the beam of electrons, wherein the communicating box is connected to the sampling box through an optical fiber, and is arranged for receiving the second signal through the optical fiber and converting the second signal into a third signal which is an electric signal, wherein the controller is arranged for receiving the third signal. wherein the electron accelerator is arranged for emitting and accelerating a beam of electrons, wherein the electron beam focusing device is located at a rear end of the electron accelerator and comprises a beam restraining rail and 2n+1 sets of magnetic poles (1-4, 5-8, 9-12) wherein the beam restraining rail forms a beam restraining channel through which the beam of electrons are to pass, wherein the 2n+1 sets of magnetic poles are installed on the beam restraining rail and are distributed at different locations of the beam restraining channel, wherein an nth set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a first direction, wherein an (n+1)th set of magnetic poles of the 2n+1 sets of magnetic poles are arranged for performing, on the beam of electrons, focusing in a second direction, wherein the second direction is perpendicular to the first direction, wherein the n is a positive integer, wherein the system further comprises an electron beam detecting device arranged for detecting the beam of electrons, wherein the electron beam detecting device comprises an electron collecting device, a shield room, a communicating box, and a controller, wherein the electron collecting device is located together with the electron accelerator inside the shield room, and is arranged for acquiring a first signal by detecting a strength of the beam of electrons radiated by the electron accelerator, wherein the communication box is located outside the shield room, wherein the controller is located outside the shield room, is connected to the communication box, and is arranged for controlling detection of the beam of the electrons; characterised in that the electron beam detecting device further comprises a sampling box, wherein the sampling box is located inside the shield room, is connected to the electron collecting device, and is arranged for receiving the first signal and converting the first signal into a second signal which is an optical signal that reflects a degree of uniformity of irradiation of the beam of electrons, wherein the communicating box is connected to the sampling box through an optical fiber, and is arranged for receiving the second signal through the optical fiber and converting the second signal into a third signal which is an electric signal, wherein the controller is arranged for receiving the third signal. wherein the communicating box is connected to the sampling box through an optical fiber, and is arranged for receiving the second signal through the optical fiber and converting the second signal into a third signal which is an electric signal, wherein the controller is arranged for receiving the third signal.