Abstract: Using Meta-analysis,the article analyzed the effect of mannan oligosaccharide on weight gain rate,specific growth rate and feed coefficient of fishes,then expounded whether mannan oligosaccharide could play a promoting role on fish growth,and provided a scientific reference to the health of the fish breeding. Using the computer retrieval CNKI database,collecting literatures about the growth promoting effect of mannan oligosaccharide to fish,the paper extracted the data and made Meta-analysis on literature that met the standards. Results:A total of 12 studies were included.The results of Meta-analyses showed that the weight gain rate and specific growth rate of experimental group significantly improved than controlled groupMD=24.77,95%CI=(11.92,37.61),P<0.000 01 MD=0.10,95%CI=(0.07,0.13),P<0.000 01,while the food coefficient of fish of experimental group was significantly below than controlled groupMD=-0.16,95%CI=(-0.24,-0.08),P<0.000 01. Conclusion:Mannan oligosaccharide could significantly improve the fish weight gain rate and the specific growth rate,and significantly reduce the food coefficient of fish.