The research was conducted in the watershed area of Mamasa. Data was taken for 11 months starting from December 2006 to October 2007.The research aimed to identify the influencing factors of the river discharge which were decreasing from time to time. Data was collected through the application of direct field observation and literature study. Data on precipitation were gained from 4 stations. The stations were located in Sumarorong, Mamasa, Minake, and Pana. Data regarding the river discharge were taken from the office of The Water Source Management in south Sulawesi Province. Meanwhile, data of land cover were gained from GIS mapping taken in 1999 and 2003 as well as from Spot 4 in 2007. Data were analyzed by regression linear model to identify the effect of independent variable to dependent variable.The results of the research show that the changes in river discharge fluctuation were influenced by precipitation and land cover factor. The dominant factor that influenced river discharge fluctuation were conifers and wide leaf type of vegetations. Data were analyzed by regression linear model to identify the effect of independent variable to dependent variable.The results of the research show that the changes in river discharge fluctuation were influenced by precipitation and land cover factor. The dominant factor that influenced river discharge fluctuation were conifers and wide leaf type of vegetations. Key words: watershed, influencing, fluctuation Key words: watershed, influencing, fluctuation