Abstract: In order to investigate the effects of salinity changes on the growth of juvenile Hippocampus kuda during the breeding process, eight salinity gradients (17S, 19S, 21S, 23S, 25S, 27S, 29S and 31S) were set in this experiment. With 25S as the control group, the external behavior and internal physiological, biochemical and genetic parameters were analyzed when the salinity of breeding was changing in a short-term. External behavioral indicators include feeding response time, feeding rate, and food intake etc. were closely related to the amplitude and rate of salinity change. The internal physiological and biochemical parameters that were analyzed in this study included the activity or concentration of SOD, CAT, MDA, AKP, ACP, Trypsin, LPS and AMS. Changes in the expression of related function genes, such as SOD, Hsp70, Hsp90, Gst, Pyy, Mtor, Bcl-2, Casp9, Casp3, Gadd45α, Fadsd6, Cpt1, Fas, Cyp51, Pdha1, Mdh1, Idh3b and G6pd were also monitored. The results showed that, the feeding behavior of juvenile H. kuda was regular changes under the influence of short-term salinity changes, feeding reaction time was prolonged, feeding rate and food intake were reduced, suggesting that the juvenile’s nutrition intake decreased, meanwhile, the changes of AMS activity and MDA concentration showed a significant correlation with the reaction time, food intake of feeding behavior and the gene expressions of Gadd45α, Idh3b, SOD, Cpt1 and Pyy also had a close correlation with the behavioral parameters simultaneously. The result could become an important potential combined biomarker to reveal the responses and relationship of H. kuda in vivo and in vitro under the salinity stress, which can reflect the salinity effects on the growth of juvenile seahorse. The external behavioral changes can correctly reflect the excessive fluctuation of salinity which is harmful to the juvenile seahorse.