Enterprise-owned power plants have been increasingly built in China recently. With a real-world case, this paper presents a comprehensive procedure to deal with the stability and security assessment of such a power system. On software platform of ETAP, eleven typical load-flow operation points are set up as base cases for static analysis and short circuit analysis, stability and security assessment. Transient stability is simulated for fault contingencies at each bus and each branch. By this way, the features of the system operation and stability are explored. Accordingly measures concerned with excitation system, special protections, operation structures, are proposed to enhance the stability and security of the power system.