Software process modeling has become an essential technique for managing software development processes. However, purely quantitative process modeling requires a detailed understanding and accurate measurement of software process, which relies on reliable and precise history data. This paper presents a semi-quantitative process modeling approach to model and manage software development processes. It allows for the existence of uncertainty and contingency during software development, and facilitates a manager’s qualitative and quantitative estimates and assessments of process progress. We demonstrate its value and flexibility by developing semi-quantitative models of the test-and-fix process of incremental software development. Results conclude that the semi-quantitative process modeling approach can support process or project management activities, including estimating, planning, tracking and decision making throughout the software development cycle.