【Objective】Biochar amendment to soil has recently been considered as a promising strategy to improve soil carbon sequestration and soil fertility. The aim of this work was to investigate effect of biochar on plant growth and its potential mechanism behind, so as to provide a theoretical reference for the use of biochar as a soil amendment in agricultural soils to improve soil fertility and enhance soil carbon sequestration. 【Method】 For this study a pot experiment was performed to investigate changes in ryegrass growth, soil microbial community abundance and soil enzyme activities involved in C, N and P recycling as affected by biochar addition. The biochar used in the pot experiment was prepared out of wheat straw through pyrolysis at 350~550℃with limited oxygen, and the soil in the pots was collected from farmlands in the Tai Lake Region. Biochar was amended into the pots, separately, at a rate of 0% for Treatment C0 or control (biochar / soil in weight), 2% for Treatment C1 (low rate) and 4% for Treatment C2 (high rate) and each treatment had 3 replicates. Ryegrass (Lolium perenne) was planted in each pot and let grow for 90 days. At the end of the period of growth, ryegrass was analyzed for biomass and soils for properties, microbial community abundances and soil enzyme activities with the quantitative real-time PCR and microplate fluorimetric assay, respectively. 【Result】Results show that biochar at a low rate did not increase ryegrass biomass, but at a high rate it did significantly or by 68%. Biochar addition, low and high significantly increased soil pH, soil organic carbon (SOC), total nitrogen (TN), C/N ratio and available K content by 9%, 45% , 19%, 20%, and 104% and by 13%, 99%, 32%, 50%, and 187%, respectively, as compared with the control, whereas it decreased available N content by 17% and 18%, respectively. Besides, biochar addition, low and high also increased bacterial and archaeal 16S rRNA and nifH gene copies by 30%, 36%, and 72%, and by 50%, 83%, and 116%, respectively, and also significantly increased β-glucosidase (BG), β-D-cellobiosidase (CB), β-xylosidase (XYL), N-acetyl-β-glucosaminidase (NAG) and phosphatase (PHOS) by 25%, 118%, 123%, 112% and 14%, and by 61%, 215%, 148%, 114%, and 20%, respectively, but had no effect on leucine aminopeptidase. In most cases, no significant differences were observed in chemical and biological properties between the treatments high and low in addition rate. Correlation analysis demonstrates that abundances of all soil microbes (except for fungi) were positively related to pH, SOC, TN, C/N and activities of most soil enzyme (except for leucine aminopeptidase). 【Conclusion】In summary, all the findings in this study suggest that biochar addition can improve soil fertility, key microbial communities in abundances and enzymes in activity, which may be the major causes of biochar enhancing soil nutrient transformation functions and plant productivity.