The application provides a system for measuring a deviation value between different printing heads of a 3D (Three-Dimensional) printing device. The system comprises a positioning mechanism and a deviation value measuring mechanism, wherein the positioning mechanism comprises a base, a sleeve, a spring, a sleeve inner rod and a positioning ring; the base is mounted on a printing platform; a boss isformed in the middle part of the base; a center hole is formed in the center of the boss; the center hole is provided with a central hole upper part and a center hole lower part; the sleeve is arranged in the center hole upper part to cooperate with the center hole upper part in an interference manner; the spring is arranged in the central hole lower part; the sleeve inner rod is arranged in thesleeve; the lower end of the sleeve inner rod is connected with the upper end of the spring in a butting manner; the positioning ring is detachably arranged at the upper end of the sleeve inner rod; the positioning ring is provided with a guiding part on the upper edge of the outer circumferential wall of the positioning ring, and is provided with an inner limiting part along the upper edge of theinner circumferential wall of the positioning ring; the outline of the inner limiting part is at least partially matched with the outline of a to-be-determined printing head. The deviation value measuring mechanism comprises a rotary encoder and a display, and the rotary encoder is connected with step motors for driving the printing platform and the printing heads of the 3D printing device to relatively move.