An operation method of a multi-bits read only memory includes a step of applying a gate voltage to a conductive gate, a first voltage to a first electrode, and a second voltage to a second electrode. The multi-bits read only memory of the present invention includes a substrate and a transistor structure with the conductive gate mounted between the first electrode and the second electrode, a first oxide located between the first electrode and the conductive gate, and a second oxide located between the second electrode and the conductive gate. The present invention creates an initial state wherein the transistor structure is not conducting, an intermediate state wherein the first oxide is punched through by the first voltage, and a fully opened state wherein both the first oxide and the second oxide are punched through. The aforementioned states allow storage of multiple bits on the read only memory.