A guide ring sensor, comprising a fixing seat (10A, 10B) and a guide ring pivoted on the fixing seat (10A, 10B) by a positioning member, the guide ring having an upper section, a lower section deposited below the upper section of the guide ring, a pivot hole formed through the upper section of the guide ring, and a slot formed through the lower section of the guide ring, wherein the pivot hole of the guide ring is deposited above the slot of the guide ring, the positioning member is inserted through the pivot hole of the guide ring, and the guide ring is rotatably mounted on the fixing seat (10A, 10B), characterized in that the guide ring sensor comprises: the fixing seat (10A, 10B) having a body (11A, 11B) having a front surface; a first end of the body (11A, 11B) formed on the front surface of the body (11A, 11B); a second end formed on the front surface of the body (11A, 11B) and being opposite the first end of the body (11A, 11B); a connecting plate (12A, 12B) mounted on the first end of the body (11A, 11B); and a positioning hole (13A, 13B) formed through the body (11A, 11B) adjacent to the second end of the body (11A, 11B), wherein the positioning member is inserted through the positioning hole (13A, 13B) of the body (11A, 11B); an elastic member mounted on the body (11A, 11B) of the fixing seat (10A, 10B) and connected to the guide ring, wherein the elastic member provides resilience to the guide ring; and a sensing element mounted on the connecting plate (12A, 12B) of the fixing seat (10A, 10B) and having a sensing portion, wherein the sensing portion detects a pivoting angle change of the guide ring and the sensing element generates a signal corresponding to the pivoting angle change of the guide ring. the fixing seat (10A, 10B) having a body (11A, 11B) having a front surface; a first end of the body (11A, 11B) formed on the front surface of the body (11A, 11B); a second end formed on the front surface of the body (11A, 11B) and being opposite the first end of the body (11A, 11B); a connecting plate (12A, 12B) mounted on the first end of the body (11A, 11B); and a positioning hole (13A, 13B) formed through the body (11A, 11B) adjacent to the second end of the body (11A, 11B), wherein the positioning member is inserted through the positioning hole (13A, 13B) of the body (11A, 11B); a body (11A, 11B) having a front surface; a first end of the body (11A, 11B) formed on the front surface of the body (11A, 11B); a second end formed on the front surface of the body (11A, 11B) and being opposite the first end of the body (11A, 11B); a connecting plate (12A, 12B) mounted on the first end of the body (11A, 11B); and a positioning hole (13A, 13B) formed through the body (11A, 11B) adjacent to the second end of the body (11A, 11B), wherein the positioning member is inserted through the positioning hole (13A, 13B) of the body (11A, 11B); an elastic member mounted on the body (11A, 11B) of the fixing seat (10A, 10B) and connected to the guide ring, wherein the elastic member provides resilience to the guide ring; and a sensing element mounted on the connecting plate (12A, 12B) of the fixing seat (10A, 10B) and having a sensing portion, wherein the sensing portion detects a pivoting angle change of the guide ring and the sensing element generates a signal corresponding to the pivoting angle change of the guide ring.