This research studied the quantity of dissolved organic carbon of Sritang reservoir in order to find the relationship between general parameter of water quality and dissolved organic carbon for trihalomethane potential formation (THMFP) prediction. The result showed showed the quality of raw water with mean temperature30.1 oC, turbidity 6.1 NTU, and neutral pH. Mean of document was 2.123 mg/ I tended to higher in rainy season from June to December because of the heavily rains. the correlation analysis showed that turbidity was the best parameter correlated with document (R2=0.76), which is important precursor of trihalometanes formation. then, this studied concluded turbidity was simple parameter could predicted document and Trihalomethane Formation Potential , that useful tap water operator to manage raw water source and to use appropriate water treatment in order to minimized disinfection by products.