The Study was conducted in the Arjunsagar Reservoir of Dist. Mahoba U.P. in April 2017 to Jan 2018.Two sites and three seasons were selected for research i.e. Pre-monsoon, Post -monsoon and winter, Primary Productivity was calculated by light and dark bottle method and GPP, NPP & CR were calculated. The GPP was found Max in the month of Oct from S-1 is 1.187 and from S-2 1.156 mgC/l/d (1.1715±0.0155) and min in month of May 0.025 mgC/l/d from S-1 and June from S-2 0.025 mgC/l/d (0.3435±0.0625). NPP was max in the month of Oct from S-11.0931 & in Sep from S-2 1.062 (1.062±.031) and min in month of June from site S-1 0.062& S-2 is.184 (0.123±.061) respectively, where as CR was found max in May from site S-1 is .937 & in Jan S-2 is 0.312 mgC/l/d (0.4995±.4375) and found min in Sep from S-1 0.031 and were S-2 is 0.062 (0.062±0.031) in month of May and June.