Abstract: With the increasing demand for food, a large amount of nitrogen fertilizer is applied into soil to improve yield, but the low nitrogen use efficiency resultes in serious soil nitrogen leaching and water pollution. Biochar application into soil is considered as an effective measure to reduce nitrogen leaching. In this study, five treatments were set up in the laboratory soil column simulation leaching experiment, i.e., only nitrogen fertilizer (B₀), nitrogen fertilizer %2B 1% fresh biochar (B₁), nitrogen fertilizer %2B 4% fresh biochar (B₄), nitrogen fertilizer %2B 1% aged biochar (Ba₁), nitrogen fertilizer %2B 4% aged biochar (Ba₄) were applied, and rapeseed was planted on soil column. The effects of fresh and aged biochar at different application amounts on soil nitrogen leaching and nitrogen uptake of rapeseed were investigated in the plant-soil-leaching system. The results showed that with the aging of biochar and the increase of application amount, soil nitrogen retention and rapeseed nitrogen absorption capacity increased, and the concentration of nitrogen in leaching solution decreased, indicating that biochar has a long-term effect on soil nitrogen leaching inhibition. The results can provide the theoretical basis for reducing soil nitrogen leaching by applying proper amount of biochar.