Nitrogen and Phosphorus are the essential nutrients limitation factor for growth of phytoplankton in freshwater ecosystem. This study aimed to test the nutrients limitation factor for growth of phytoplankton in the net cages of Chi river at Dindum village where located in Mahasarakham province. In December 2014, for checks quality of the water and bioassay checks in the lab room. By divided in 4 experiments sets, those addict nitrogen (N), phosphorus (P) and nitrogen and phosphorus (N and P) and the control experiments. The result showed that, the water quality in the net cages has water temperature 28.5 °C, pH 7.18, electrical conductivity 655 µS/cm, dissolved oxygen volume 8.55 mg/l, transparency 30 cm, The concentration of ammonia (NH3) – nitrogen (N) 0.34 mg/l, the concentration of nitrite (NO2) and nitrate – nitrogen (NO2-N) 1.02 mg/l, the concentration of orthophosphate – phosphorus (P) 0.038 mg/l. The experiments sets, those addict nitrogen (N), phosphorus (P) and nitrogen and phosphorus (N and P) have the amount of A chlorophyll 1.52 µg/l, 1.39µg/l and 1.13 µg/l. The phytoplankton growth increase in experiments with the addition of nutrients when prepare with the control experiments, it showed that Nitrogen and Phosphorus are the limitation factor in the water column.