The utility model provides a water-retaining drainage sleeve of a lathe spindle. The water-retaining drainage sleeve comprises a body and is characterized by further comprising a lengthening portion and a drainage groove, the lengthening portion is fixedly connected with the body, and the drainage groove is positioned on inner walls at bottoms of the body and the lengthening portion. The water-retaining drainage sleeve has the advantages that an arm of the body is lengthened to arrange the lengthening portion, the lathe spindle is fully covered, a good retaining function is achieved, water and fluid spilled from the lathe spindle can be retained by the lengthening portion completely, and potential risks are reduced; and the drainage groove is opened on the body and the lengthening portion, collected water and fluid are led to a water tank completely through the drainage groove, problems such as blocking can not occur, and the water-retaining drainage sleeve is safe and reliable.