The invention discloses a method and system for measuring the contact force of a satellite-borne slip ring based on the cantilever beam theory. According to the method, the contact force of the satellite-borne slip ring is indirectly and accurately measured, namely, a measuring point is set near a contact point between an electric brush wire and the electric conductive slip ring, a relational expression between the initial measuring force exerted on the measuring point and the contact pressure at the contact point is elicited according to a deflection curve equation of a uniform-section straight girder, monadic regressive analysis is conducted on data measured at the measuring point through the least square method according to the linear rule of deformation, so that the accurate initial measuring force is obtained, the contact force is obtained, and the measuring accuracy is high. The system for measuring the contact force is composed of the electric conductive slip ring, the electric brush wire, a loading lifting hook, a force sensor, a displacement sensor, a connecting board, an accurate electric control motion table, a motor driver, a motor control card, a multichannel data acquisition card, a current sensor, an industrial personal computer and a displayer. Design is ingenious, operation is convenient and measurement is accurate.