The present invention discloses an electric propulsion plume deposition effect measurement device based on magnetic deflection. The device comprises a QCM pollution measurement sensor, an N-pole magnet and an S-pole magnet, a QCM installation support, a front damper support and two side support plates, wherein three sets of the arranged parts in parallel are mutually connected to form a closed measurement chamber. The QCM pollution measurement sensor is arranged on the installation support, the two magnets are distributed at the upper portion and the lower portion of a measurement chamber, themiddle portion of the front damper support is provided with a measurement limitation hole, the size of the hole is determined by measurement of an effective area and an intersection point of a measured thruster field connection line and the front damper plate through the QCM to ensure that deposition pollutants from the incoming flow of the thruster are deflected to outwards under the action of amagnetic field after charged particles pass through the measurement limitation hole, the magnetic field does not change the energy of the particles, and the particles are bombarded on the right-sidesupport plate. The electric propulsion plume deposition effect measurement device can effectively filter the sputtering effect of backflowed CEX ions to the test materials and cannot increase the energy of the CEX by employing magnetic deflection, graphite anti-sputtering materials are installed at the right-side support plate so as to greatly reduce the influence of secondary sputtering on pollution measurement.