The water quality monitoring index and frequency of typical terrestrial ecosystem on the Chinese Ecosystem Research Network (CERN) were reviewed. Furthermore, the water pH and salinity of the 31 typical terrestrial ecosystems from 2004 to 2006, of the 6 lake and bay ecosystems during 2003-2007, and of one urban ecosystem during 2008 were assessed. The results showed: 1) The pH and salinity of the CERN forest ecosystems decreased from northern to southern ecosystems and from western to eastern ecosystems. The lowest pH value was in the southeast Dinghu forest ecosystem (4.15), while the pH value ranged from 6.01 to 8.26 in the other forest ecosystems. The salinity ranged from 33 to 322 mg/L in the forest ecosystems.2) The pH and salinity of the CERN agriculture-, oasis-, and marsh-ecosystem had obvious spatial trends, with the higher values in the North China Plain, Northwest oasis and desert area, the lower values in the northeast agricultural area and the lowest values in the southern agricultural area. The pH ranged from 6.70-8.45 except those in Sanjiang marsh ecosystem and southern agricultural ecosystems with the lower pH values. The higher salinity values (more than 500 mg/L) were mainly in the western oasis and Yellow River floodplain agricultural ecosystems.3) The pH in the lake, bay and Beijing urban underground water were ranged from 6.8-8.8. There is little seasonal variation of pH in bay site but significant seasonal variation of pH and electrical conductivity in the lake sites and Beijing urban underground water. In the lake sites, the pH values were higher in summer and autumn, but the electrical conductivity values were lower during June to September. While in the underground water of Beijing urban site, the pH values were lower during May to October, while the salinity (electrical conductivity) values were higher during May to July. The study suggests that the advanced in-situ remote sensor technique, with high monitoring frequency, is needed to monitor the water pH and electrical conductivity. Furthermore, in order to differentiate the seasonal variation with long term trend and clarify the natural variation with the human being effects on water quality, it is necessary to continue long-term monitoring and undertake short time investigation in catchment or regional scales, and consider the human effects (acid deposition, agricultural fertilization, irrigation and drainage, point or non-point source pollution,etc.) on water quality.