The utility model discloses a tool for detecting circle run-out of a rotary joint in the field of drilling pumps, relates to the technical field of drilling pumps, and aims to solve the technical problems that a rotary joint manufacturing unit exits a factory to check the circle run-out of the rotary joint, and whether the circle run-out of the rotary joint is qualified or not when the rotary joint purchased by a using unit enters the factory to check. The technical scheme adopted by the utility model is as follows: only a drilling pump rack part for simulating a
crankshaft mounting hole is required, a drilling pump
crankshaft end part is simulated, and the drilling pump
crankshaft end part is simulated; the tool for detecting the circle run-out of the rotary joint in the field of the drilling pump is composed of other simple parts and standard parts such as bolts and nuts, the structure is simple, the cost is low, and the technical problem of detecting the circle run-out of the rotary joint in the field of the drilling pump can be solved.