— Software evolution and update play a vital role in software engineering. It has many advantages, such as improving the efficiency of programming, reducing the cost of maintenance and promoting the development of software systems. This paper further analyzes the evolution and update processes of three typical kinds of real-world object-oriented software systems by using the tools of complex networks. It discovers some underlying dynamical evolution characteristics and rules of the object- oriented software systems. These results are very useful for the design and development of the objectoriented software systems.