The ability to monitor and manage a large scale distributed system is very crucial for the reliable operation of the system. The monitoring data can be used to determine the source of performance problem, tuning up both application and system software, detect and recovery fault, and support advance services such as prediction system (NWS), Grid scheduler, and accounting service. This presentation focus on the discussion of a project called Grid Observer. The goal is to develop technology and software tools that allows system administrator to monitor the state of large distributed system and grid computing system. The design of this system focuses on some key areas, such as the well defined and repetitive structure, the ease of use, and the capability to form a hierarchical monitoring infrastructure. The system has currently been installed and used by many sites including the APGrid test bed (www.apgrid.org/scmsweb). More information can be found at http://observer.cpe.ku.ac.th.