Abstract: The aims are to learn the effect of eugenol on fish culture, and determine whether the stress response may be reduced by moderate anesthesia. By proper anesthesia and no anesthesia on Tilapia mossambica, the dynamic changes of cortisol and lactic acid in T. mossambica plasma after treatment in different periods were tested. The results showed that when the concentration of eugenol gradually increased within the range of 10-120 mg/L, the duration of anesthesia was gradually shortened, and the recovery time gradually increased, and the best concentration was 45 mg/L. Samples were taken after 0, 30 and 60 min, the concentration of cortisol in eugenol group was reduced, while there was no significant difference at different time (P>0.05) and that in the contrast group was obviously increased (P<0.05). The cortisol concentration of eugenol group at 0 min was lower than that of the contrast group and significantly lower than that of the contrast group (P<0.01) at 30 and 60 min. The lactic acid concentration in the two groups almost remained the same at 0 min, and that in contrast group at 30 min and 60 min was greatly higher than that at 0 min (P<0.05), and obviously higher than that of the eugenol group at 0, 30 and 60 min (P<0.05), therefore, the difference of lactic acid concentration in the eugenol group was slight. It indicates that with ideal anesthetic dose, eugenol can effectively avoid the increase of cortisol and lactate acid concentration, and reduce capture stress of T. mossambica.