The invention belongs to the technical field of lathe turning machining tool fixture appliances, and particularly relates to an internal expanding type lathe turning machining tool. According to the internal expanding type lathe turning machining tool, the internal expanding type lathe turning machining tool comprises a tool body, a tool pulling rod and expanding blocks. An inner hole is formed in the tool body in the axial direction. The tool pulling rod is assembled in the inner hole of the tool body and pushes the expanding blocks to do radial movement, so that a product is loosened or tightly held. The internal expanding type lathe turning machining tool has the beneficial effects that the tool is suitable for producing pipe joints and pipe fittings of which the wall thickness of the products is small and the categories of the company products are diversified, clamping is convenient, loading and unloading of workpieces are rapid, the clamping time of the products can be greatly shortened, the operation labor intensity of workers is relieved, the tight locking force is made to be kept consistent all the time, and the situation that the products are clamped and deformed to be scrapped due to large strength exerted in other clamping modes is avoided.