The invention discloses an electromagnetic unlocking structure for in-orbit unfolding operation of a spacecraft detection device mechanism. The electromagnetic unlocking structure for the in-orbit unfolding operation of the spacecraft detection device mechanism comprises a cover plate and a mounting plate for holding a detector, a pivot on one side of the cover plate is rotationally connected onto the mounting plate, a pair of torsional springs are symmetrically arranged on the pivot so as to keep the pivot in unfolded state by torsional force after the cover plate is unfolded, a first iron core body is mechanically fixed on the other side of the cover plate, a permanent magnet is arranged in the middle of the first iron core body, an M-shaped second iron core body is arranged on opposite sides of the mounting plate and the cover plate, three protruding portions of the second iron core body are in corresponding face contact with two ends of the first iron core body and the permanent magnet, and an electromagnetic coil is capable of generating electromagnetic force larger than attraction force after being electrified by unlocking current so as to unlock the spacecraft detection device mechanism and keep the unlocking state under the action of spring force of spiral springs. The electromagnetic unlocking structure for the in-orbit unfolding operation of the spacecraft detection device mechanism is light in weight, small in size, low in energy consumption and capable of unlocking and unfolding the spacecraft detection device mechanism quickly and reliably and keeping the unlocking and unfolding states.