To improve the efficiency of network fault management system, an improved FNG state machine is introduced in original CFM technology. Special fault shielding mechanism with alarm mechanism of the priority level is added. The fault life duration and fault reproduction duration are set. The priority level is determined before printing alarm messages. In running, the user interface of the system could print alarm messages with 3 grades, and will not repeatedly print the same warning. Testing results show that the improved FNG state machine can reflect the high-level alarm and single display repetitive fault alarms. It won't show transient fault alarms, thereby reduces the labor mount of network administrator to locate fault, and improves work efficiency.