The anesthetic effect of Datura seed extract was evaluated on 15 pieces of young Cyprinus carpio weighing approximately 25 to 50 g. In order to determine the effectiveness of L. Datura stramonium extract on the importance and severity of Cyprinus carpio  anesthesia in doses between zero mg to 10 mg /L, 10 treatments (zero treatment, control) were devised with the identical conditions (pH 7/2, temperature 22 °C, extract and fish). When fish were placed in different treatments in the drug bath, the onset time of anesthesia, the time of complete anesthesia, deep anesthesia and mortality percentage were measured by a chronometer. The results showed that increasing the concentration of Datura extract reduced the onset time of anesthesia. There was a significant difference between the onset time of anesthesia in the range between 6 mg /L and 8 mg / L (p≤0.05), There was no significant difference between 6 and 7 mg / L and 7 and 8 mg / L (p>0/05). There was also a significant difference between the mean time of complete anesthesia between 6 and 8 mg / L treatments (p≤0.05) but there is no significant difference between 6 and 7 mg / L and 7 and 8 mg / L (p>0/05). With increasing drug concentration, the mean return time from anesthesia in the treatments was different and a significant difference was observed between 6 and 8 mg / L (p ≤0.05).