Persian Gulf is known as one of the main areas of oil exploration and production, and in the meanwhile, this causes some problems for the contained water ecosystem by pollution. In this concern, one of the ways to face this problem is the use of oysters as biological treatment. Sacostrea cucullata is one of endemic oyster species to Persian Gulf that is known as one of the important filterers. The main goal of this study is to define the absorption amount of Cadmium (150 µg/l) and Copper (200 µg/l) by this species in complete natural conditions. A mesocosm system was designed for this purpose. The results showed that the refining rate is affected by the amount of Cadmium (from 1.69 ml/min.g AFDW to 0.04 ml/min.g AFDW) and Copper (from 2.16 ml/min.g AFDW to 0.42 ml/min.g AFDW) in an hour period in which it was still continuous. Despite the clearance rate was significantly reduced, however, live oysters reduced the amount of Cadmium and Copper from 150 and 200 µg/l to 118.68 and 133.30 µg/l respectively. It also has been depicted that the dead shells have a good ability to reduce the metal condensation. According to the results it can be concluded that Sacostrea cucullata can be used as biofilters with good clearance ability.