Abstract: In order to explore poplar high-yield water and fertilizer condition, the effect of humic acid and inorganic fertilizer on poplar growth and soil fertility were conducted under low, normal and high three different water levels by pot experiment. The result showed that: there was no significant difference on the dry weight under low water treatment between the application of humic acid and inorganic fertilizer, but had significant difference under regular and high water treatment. Under the three different water levels, total average dry weights were 14.60 g, 96.03 g and 230.00 g respectively which had significant difference between them. Compared with inorganic fertilizer under the same water levels, the application of humic acid significantly decreased the contents of nitrate nitrogen and available P, K, increased the content of ammonium nitrogen; significantly increased the contents of total C and correspondingly the humus activity; and had significantly enhanced the activity of polyphenol oxidase enzyme, but had little effect on catalase enzyme. As for the urease enzyme, the application of humic acid significantly increased urease enzyme in the low and regular water treatment, and had no significant difference in the high water treatment. To sum up, application of humid acid were blocked under low water treatment, but it had significant effects on poplar growth and soil fertility under regular and high water treatment.