Grid based computational infrastructure is a promising next generation computing platform for solving large-scale resources- intensive problems. With the developing Grid technologies and applications, the research on the Grid monitoring system gets increasingly essential and significant. As far as the present research are concerned, there exist two mainly technologies in grid performance monitoring: MDS (monitoring and directory service) and GMA(Grid Monitoring Architecture). In this paper the author puts forward a novel Mobile Agent-based Grid Monitoring Architecture (MA-GMA), which introduces the mobile agents and cache mechanism of MDS. Based on the Open Grid Service Architecture (OGSA) standard, we merge the characteristics of intelligence and mobility of mobile agent into the current OGSA to construct a dynamic and extensible monitoring system. In the end, we do some experiments under different environments. From the results of experiments shown, this MA-GMA is proved to be effective and improves the monitoring performance greatly.