The objective of experiment to investigate the potency of bacterial strain on improving the quality of slaughterhouse wastewater. Studies on biodegradation of COD, BOD, high protein and fat by selected enzyme producing bacteria were carried out in slaughterhouse wastewater with mixed culture of bacterial strain. At lab scale, It was found that, treatment with bacterial strain resulted in COD, BOD, protein and fat removal to the great extent as compared to the results of treatment without bacterial strain. From the lab scale results, it is clear that; the microbial strain is very useful in improving the treatment efficiency. So, the performance evaluation of treatment plant has been studied with the application of this bacterial strain in aerobic system of slaughterhouse ETP. The Final effluent shows, the desirable per cent reduction with respect to COD, BOD, protein and fat. The efficiency is achieved by enzymatic reaction of bacterial strain producing different types of enzymes and it catalyses various reactions within secondary aerobic treatment. Treated final effluent quality was also evaluated by using toxicity test/ fish bioassay with test fish Lebistes reticulates.