Abstract: The Acetanilides herbicide acetochlor has been applied extensively in soybean field. There is mostly dry and with low temperature in the spring in Heilongjiang province, and it makes the efficacy of acetochlor can't develop steadily, but usually appears injury to soybean seedling in some low-lying and damp regions. To grope for the influence of climate condition to acetochlor efficacy and injury, the influence of soil humidity to injury of acetochlor were studied by the plot experiment in May to September of 2003-2004. The results showed that the humidity influence obviously the injury of acetochlor. The injury of acetochlor in the higher humidity was the most serious, the injury of meddle humidity was slightest and the injury of dry treatment was at inter-between. The injury of acetochlor influenced evidently the growth of soybean. The soybean growth was descended obviously with the injury aggravated. The acetochlor injury to soybean is more severe, the influence to soybean growth is more graveness. The representation was some criterions decline, which was the plant height, the plant fresh weight, the root fresh weight, hundred grains weight and the soybean yield, the root became shorter, the effective bean-pod and grains number was decreased.