This paper explores the collection efficiency of Electrostatic precipitator (ESP) of a laboratory scale model which is geometrically similar to the industrial ESP of a local coal based power station. The variable fly ash velocity is used to determine the collection efficiency of an ESP. The applied voltage and current are being kept constant during different field test. Moreover a test run will be conduct to see the collection efficiency without applying high voltage. The experimental result shows that ESP collection efficiency is higher at lower fly ash velocity and suddenly decreases after a range of velocity. To confirm the validity of collection efficiency a mathematical model has been built and verified with experimental data. In addition, a test run is conducted without the high voltage (HV) supply to see the ability of capturing fly ash particles by keeping all other parameter same. The peak efficiency of ESP found in this experiment is 99.87%.