In this paper the effect of multi-function parallel active filter to improve power quality for one of Bam-in Kerman province-automotive industries (Kerman motors) is been reviewed. All the equipment with electronic control devices contains: rectifiers, modulators and switch devices which because of the material used for their semi-conductors , the consumed current of this equipment are non-sinusoidal with high distortion. By measuring the power quality in a several month period before and after installing active filter parallel to each paint substation transformers, the results indicates that the mean reduction of voltage harmonic is 55% and the current harmonic is 78%, furthermore the energy consumption in each electrolyze is reduced to 29% compared with when no filter is installed. In addition the economic calculations show that the returned investment will be in 26 month and the saving will be 253166$ in ten years.