CMM is a method to evaluate software contracting ability and help it improve software quality, focusing on the management of software development process and the improvement and evaluation of engineering ability. CMM is divided into five levels: the first level is initial level, the second level is repeatable level, the third level is definition level, the fourth level is management level, and the fifth level is optimization level.

CMM/CMMI divides the maturity of software process into five grades, and the following are the basic characteristics of the five grades:

(1) initial stage (initial). There is something wrong with the work, and the original plan is often abandoned during the project. Management is disorganized and lacks a perfect management system. The effectiveness of the development project is unstable, and the success of the project mainly depends on the experience and ability of the project leader. As soon as he left, the work order was beyond recognition.

(2) Repeatability. Management is institutionalized, basic management systems and regulations have been established, and management work has rules to follow. Standardization has been achieved initially, and the development work has been well implemented according to the standards. Changes should be made in accordance with the law, so as to be baseline, stable and traceable. The planning and management of new projects are based on past practical experience and have the environment and conditions to repeat previous successful projects.

(3) It has been defined. The development process, including technical work and management work, has been standardized and documented. A perfect training system and expert evaluation system have been established, all technical activities and management activities can be controlled, and there is a common understanding of the process, post and responsibility of the project.

(4) trusteeship. Quantitative quality objectives have been established for products and processes. Productivity and quality in development activities can be measured. The process database has been established. It realizes the control of project products and processes. Forecast process and product quality trends, such as forecast deviation, and realize timely correction.

(5) optimization. We can concentrate on improving the process and adopting new technologies and methods. There are ways to prevent defects, find out weak links and improve them. Statistical data of process effectiveness can be obtained and analyzed to get the best method.