The utility model belongs to the oil equipment manufacturing technical field, in particular to an inner hole processing tooling after an oil drilling pump guide plate is cut open; the entire tooling is shaped as a cylinder; wherein, the inner hole is meshed with the entire shape of the guide plate; a connecting hole for connecting the guide plate with the cylinder is arranged on the cylinder wall; a connecting bolt is arranged in the connecting hole; and a positioning rabbet is arranged in the inner hole of the cylinder. The tooling ensures the geometric and dimension tolerance and the processing accuracy of the inner hole of the guide plate and improves the matching performance between the guide plate and the crosshead matching curvature to ensure the matching area between the guide plate and the crosshead; besides, the tooling reduces the guide plate strain rate, saves the rework costs and reduces the repetition work of employees so as to improve the manufacturing quality of the drilling pump and reduce the production costs.