The invention discloses a positioning tooling of a product cavity, comprising a baseplate, a clamping part, a workpiece product and a positioning insert, wherein the clamping part extends out of one side of the baseplate, the workpiece product is fastened on the clamping part, and the positioning insert is used for positioning the workpiece product; the workpiece product comprises at least two processing blocks which are capable of mutually spliced and a cavity formed between the processing blocks, and the positioning insert is placed in the cavity and matched with the cavity, therefore, the processing blocks which are mutually spliced can keep favorable positioning relationship through the positioning insert, the relative displacement of the processing blocks during the processing is avoided, and the machining precision is consequentially ensured.