The invention discloses a semi-closed space thread processing method. Through adopting the combination of a universal milling head and a right-angle milling head, using a special processing technologymethod, and adopting a three-axis processing center, the work of a five-axis processing center is accomplished, the accuracy of the processed product completely meets the working requirement, and thesemi-closed space thread processing method is low in cost, has high economic benefit, and is applied to the field of thread processing methods.