Vulnerability assessment and mapping of hazard pollution is raised on as an important management strategy to protect the karst. Karstic aquifers in semi-arid regions of the West of Iran with regard to the natural conditions of the region, are susceptible to contamination. Estimation of amount and vulnerability mapping of aquifers in the karst religion of Bistoun- Paraw – Kermanshah plain against poullution emissions using the COP model are theaims of this study. This model using of three parameters - covering layer (O), concentration of flow (C) and regime of precipitation (P) - assesses the vulnerability of karst water resources against pollution. The results show that %31/4of the area has located in the zone of average vulnerability and %30/7of area has been in the low ​​vulnerability area and %37/9of the area has taken a very low vulnerabilities value. The later zone has been included  most part of the plain. Major areas of low and moderate vulnerabilityzones has been located in the high part of the area on wherethe developed limestone territory of karst formations is found. Vegetation cover of these regions areforest-steppe vegetation where is located in the low vulnerability zone and without vegetation cover where is in the moderate vulnerability zones. The latest has over 800 mm Precipitation. Totally, the Parameters that have  most important role in  vulnerability level in the areaare C, P and O respectively.