The utility model discloses a polished rod calliper belongs to the oil field. Calliper include: first calliper body, locate criss -cross second calliper body in the intersect with first calliper body, an axle that is used for at the intersect movably of department first calliper body of connection and second calliper body, the preceding tip of first calliper body is the arcuation, and the preceding tip of second calliper body is the arcuation, be connected with a locking mechanism in the inboard of the back tip of first calliper body, and be connected with the 2nd locking mechanism in the inboard of the back tip of second calliper body, be connected with first fixed column at the middle part of first calliper body, and be connected with the second fixed column at the middle part of second calliper body, there is the spring in the outside of first fixed column and the outside cover of second fixed column. The utility model discloses an outside cover at first fixed column and second fixed column has the spring, and the back tip that makes the spring bullet open the calliper body need not exerted external force for calliper and just can be reached the purpose of lifting calliper off, saves time promptly and be laborsaving.