The invention discloses a four-bar-linkage feed-screw-nut electrically-driven underwater mechanical arm gripper. The four-bar-linkage feed-screw-nut electrically-driven underwater mechanical arm gripper comprises a finger execution structure assembly, a four-bar-linkage driving structure, a feed-screw-nut transmission assembly, a motor driving system, a sealing part and a fastening part; the finger execution structure assembly is a finger-shaped structure assembly, and is used for grabbing and clamping objects; the four-bar-linkage driving structure is connected with the finger execution structure assembly, and is used for driving the finger execution structure assembly to conduct opening and closing movement; the feed-screw-nut transmission assembly is connected with the four-bar-linkage driving structure and the motor driving system separately, and is used for driving the four-bar-linkage driving structure to move; and the motor driving system is used for driving the feed-screw-nut transmission assembly to move. According to the four-bar-linkage feed-screw-nut electrically-driven underwater mechanical arm gripper, feed screw nut transmission and a four bar linkage structure are adopted, and through feed screw nut transmission, rotating movement of a motor is converted into linear movement needed for driving the four-bar-linkage structure, so that the two-finger mechanical gripper is driven to be opened and closed, and the four-bar-linkage feed-screw-nut electrically-driven underwater mechanical arm gripper has the advantages that the structure is compact, rotation is flexible, the carrying capacity is high, the four-bar-linkage feed-screw-nut electrically-driven underwater mechanical arm gripper is not liable to be jammed, and the like.