Daily rainfall data from six meteorological stations surrounded Tonle Sap Lake was used to analyze a statistical characteristic of rainfall distribution and trend analysis of extreme rainfall for both annual and seasonal. Daily rainfall indices were defined and analyzed based on the World Meteorological Organization guideline. Mann–Kendall’s and Sen’s slope estimator were used to define the statistical significance of the rainfall changes and the magnitude trends of an extreme rainfall event, respectively. As the results, statistical analysis of annual and seasonal rainfall within the study period (1985-2010) varied upon locations. In addition, the amount of rainfall in wet season contributed 84% of annual rainfall for the study period. For analysis trend of extreme rainfall showed that only a few indices at few of the stations showed statistically significant changes, the significant increasing trend of very heavy rainfall (R20mm) was found at Pursat in annual and wet season, the significant increasing and decreasing trend in dry season were found at Banteay Meanchey and Kampong Thom, respectively. Furthermore, the significant increasing trend in number of wet (NWD) and dry days (NDD) was found at two stations Pursat, Siem Reap in annual time step. Therefore, these results strongly support to the disaster management and planning through comprehensive extreme event information, regarding to the trend magnitude.