The utility model relates to an auxiliary device for locking a screw, which is provided with a tube body and a revolving member, wherein a pipeline of which both ends are connected is arranged in the tube body, the revolving member can radially rotate in the pipeline, the external diameter of the revolving member is smaller than the internal diameter of the pipeline of the tube body, and the revolving member is arranged in the pipeline. The external of one end of the revolving member is provided with an annular notch for inserting the inner side of a fixing assembly, the outer side of the fixing assembly is buckled in the annular notch in the pipeline of the tube body and restricts the axial moving of the revolving member in the pipeline, and an axis through hole is arranged in the revolving member. With the revolving member, the utility model can radially rotate in the tube body, and the long screw driver head can axially move in the through hole and assist the screw fixing on the object, and the utility model has the effect of simple and safe operation.