Biochar (BC) application can improve soil fertility, enhance crop yield and exert other positive effect. In this study, the responses of lettuce yield, quality and soil properties to chemical fertilizer nitrogen (N) reduction and BC application after one year were investigated in order to guide the reduction of chemical fertilizer application and scientific usage of BC in open field vegetable production in the Pearl River Delta region. A field plot experiment was conducted in Sanshui District, Foshan City, China, to investigate the changes in lettuce yield, quality, SPAD value and soil nutrients under five treatments, i.e., conventional N application (N100%), N reduction of 20% (N80%), N reduction of 40% (N60%), N reduction of 40%+BC of 10 t/hm² (N60%+BC10) and N reduction of 40%+BC of 20 t/hm² (N60%+BC20). Lettuce yield is significantly decreased by 13.5% under N60% treatment compared to N100% treatment. Under the condition of 40% N reduction, the application of 10-20 t/hm² BC improves lettuce yield by 9.5%-22.7%, equal to the yield of N100% treatment, demonstrating that BC application has a significant effect in improving lettuce yield. Nitrogen fertilizer reduction and BC application has inconspicuous effect on lettuce single plant weight, diameter and water content, while there are different effects on leaf SPAD values at different growth stages. The increase of N and P uptake in lettuces treated with BC under N reduction is one of the mechanisms of yield increase. Nitrogen fertilizer reduction does not significantly affect nitrate content, but reduces total polysaccharide content of lettuce. While N60%+BC20 does not affect the total sugar content but significantly reduces nitrate content by 34.6% in lettuces, which have the effect of improving the quality of lettuce. Both N reduction and BC application promote soil pH, with N60%+BC10 and N60%+BC20 treatments significantly increase soil pH by 0.48-0.65 units compared with N100%. Moreover, BC application under reduction of N conditions has the potential to enhance total soil phosphorus and organic matter contents. The application of N80% or N60%+BC10 can still improve the uptake of N and P by lettuce after one year, which ensures the yield of lettuce as well as improves the quality and refines soil of the vegetable field.