This study was accomplished to select input parameters in neural network for predicting nutrient removal efficiency using removal efficiency data to inject the artificial concentration of nutrients in high rate algal pond (HRAP). It has presented a possibility to predict nutrient removal efficiencies using neural network in HRAP and selected in CASE 1 was the best success in the decision of input parameters. The input parameters were operation periods, light intensity, hydraulic retention time, pH, total nitrogen, total phosphorus, alkalinity and suspended solid.