The invention discloses a quickly and automatically opened mobile data memory which is characterized in that the mobile data memory comprises a protective housing, a storage core body, a compression spring, a buckle and a tripping device. The cross section of the storage core body and the protective housing are waist-shaped. The storage core body is arranged in the protective housing. The storagecore body longitudinally and freely slides in the protective housing. The compression spring is fixedly mounted between the bottom end of the protective housing and the bottom end of the storage corebody. The buckle is fixedly mounted at the bottom end of the storage core body. The tripping device is arranged at the bottom end of the protective housing. The buckle is buckled with the tripping device. The top end of the protective housing is provided with an extending-out hole of the storage core body interface. Through arranging the protective housing outside the storage core body, the storage core body is totally retreated into the protective housing when the mobile data memory is not in use, thereby performing a function of protecting the storage core body and preventing outside collision or wearing.