In order to strengthen scientific management, a digital method of man-hour quota calculation based on the theory of lean production was proposed and a man-hour quota management system which is a computer-aided measurement system was researched and developed. Firstly, machine power signals were acquired and the processing state was judged after filtering. Secondly, the cutting processing time was gotten according to the processing status, which was integrated into the standard man-hour. Finally, the data was stored for future use in data mining and also for providing a reliable basis and guarantee for the accounting of product costs, the plan of production and the allocation of resources. The accurate counting of man-hour was realized in this system, which has the advantages of simple structure, low cost and practicality, and is suitable to be applied and popularized in discrete manufacturing enterprises.