【Objective】This study was carried out to investigate effects of application of nitrogen (N) fertilizer plus biochar varying in rate on soil physico-chemical properties for 30 months (9 consecutive vegetable crops) in an intensive vegetable production system. 【Method】 During the observation period from April, 2012 to October, 2014, nine crops of vegetable were successfully planted, including Amaranth (Amaranthus mangostanus L.), Water spinach ( Ipomoea aquatic Forssk.), Cilantro ( Coriandrum sativum L.), Baby bok choy ( Brassica chinensis L.) and Spinach ( Spinacia oleracea L.). The experiment was designed to have three biochar amendment rates, namely, B0 (without biochar), B1 (20 t hm^-2) and B2 (40 t hm^-2) and two N application rates, namely, N0 (No N applied) and Nc (1 233 kg hm^-2 a^-1, the same as in conventional vegetable fields and a typical case of N overdose), thus forming six treatments. In the experiment, compound fertilizer of (N):(P₂O₅):(K₂O) being 15:15:15 in ratio was applied at 313 kg hm^-2 to Amaranth and Cilantro, 600 kg hm^-2 to Water spinach and 250 kg hm^-2 to Baby bok choy and Spinach as the local farmers usually do. Soil samples were collected from the 0~20 cm, 20~40 cm, 40~60 cm, 60~80 cm and 80~100 cm soil layers of every treatment for in-lab analysis at the end of the experiment or right after the harvest of the last vegetable crop on October 30, 2014. 【Result】 Comparisons between the treatments with and without N show that N application significantly increased soil total nitrogen (TN), soil electronic conductivity (EC), bulk density and cation exchange capacity (CEC) by 9.4%~18.1%, 172.4%~241.1%, 5.6%~7.6% and 10.4%~15.0%, respectively, while significantly decreased soil pH by 0.68~1.10; Although two-way ANOVA shows that N application significantly increased the content of soil organic carbon (SOC) by 9.8%~23.4% in all the Nc treatments, except treatment NcB0 where the content the content of SOC decreased by 17.3%, which indicates that biochar helps SOC accumulation in the soil. Besides, amendment of biochar significantly increased soil TN, SOC and CEC by 1.7%~10.0%, 3.6%~48.3% and 8.1%~37.1%, respectively, while significantly decreasing soil EC and bulk density. Meanwhile, biochar significantly increased soil pH in the three N0 treatments by 0.11~0.23, while decreasing soil pH by 0.19~0.23 in the Nc treatments. In addition, interactive effects between N application and biochar amendment on soil TN, SOC and EC were significant according to the two-way ANOVA analysis. Soil NH₄⁺-N and NO₃^--N content in the experiment varied in the range of 6.6~59.3 mg kg^-1 and 23.8~51.3 mg kg^-1, respectively. N application significantly increased NH₄⁺-N and NO₃^--N concentrations in all soil layers of the vegetable soil profiles. They varied with soil depth, and mineral N concentration, too, in a similar trend, that is, declining first and then rising with soil depth in the soil profile; Meanwhile, application of biochar significantly decreased NH₄⁺-N concentration in the 20~40 cm、60~80 cm and 80~100 cm soil layers by 4.9%~47.9 %, while increasing NH₄⁺-N concentration in the 0~20 cm soil layer; Meanwhile, it also significantly increased NO₃^--N concentration in the top soil layer by 2.4%~29.8% while did reversely in all the deeper soil layers. Moreover, biochar amendment significantly increased the vegetable yield and PFPN (N partial factor productivity) by 7.7%~43.8% and 21.8%~43.8% (p<0.01), respectively, and a significant and positive relationship of crop yield was observed with soil TN and SOC during the experimental period (p<0.01). 【Conclusion】As biochar amendment combined with N application can improve soil fertility and reduce the NO₃^--N concentration in vegetable soil, the practice may serve to guarantee healthy development of the intensive vegetable production system, and the treatment of amending 40 t hm^-2 biochar to application of N at the conventional rate is recommended to be an optimal treatment in this study.