The invention discloses a cutter mechanism for a cotton cutting roller of a cotton cutting machine. The cutter mechanism comprises electromagnetic boxes and blades, a mounting notch is formed in the middle of each blade, two sides of the mounting notch of each blade are respectively provided with an inclined limit guide rail, the blades are mounted in a tool rest through the mounting notches and the limit guide rails, a row of hooked cutter teeth are arranged on the blades, each blade corresponds to one electromagnetic box, the electromagnetic boxes are mounted in the cotton cutting roller, a power supply and an electromagnet are arranged in each electromagnetic box and connected with each other through a connecting line, the electromagnets are connected with metal contact ends of the corresponding blades through connecting lines, a contact spring of each electromagnet is positioned on one side of the metal contact end of the corresponding blade, one side of the metal contact end of each blade is connected with an elastic piece, the other side of each elastic piece is connected with an electrode, and each electrode is connected with the corresponding power supply through a connecting line. An existing cutter mechanism for a cotton cutting roller of a cotton cutting machine is improved, and original inertial cotton cutting is changed into electromagnetic clutch drive cutter vibrating cotton cutting, so that cotton cutting strength and efficiency are improved.