Abstract. This study was conducted to demonstrate the effect of plant extracts from the Nerium oleander L. plant and ultrasound waves of different frequencies (10-50) (20-45) (50-60) (30-65) KHz on the barnacle larvae cyprid of barnacle Balanus amphitrite amphitrite obtained from Nasiriya Thermal Power Station inlet water. Samples were collected bimonthly three replicates. The results of the Oleandrin 1 and 2.5 mg/500 ml showed a an effect of losing the larvae cyprid, 2.5 mg showed an increasing effect on the seventh day. A maximum losing of larvae cyprid was attained when using ultrasonic with con junction of 2.5 mg Oleandrin extract reached 100% on the tenth day