The aim was to study the effect of different peanut shell biochar(0%，0.5%，1%，2%，4%)on the Pakchoi(Brassica rapaL.chinensis)growth and nitrogen use efficiency in red and fluvo -aquicsoil.We used the leachingcolumns，root scanner and analysis software to identify the Pakchoi biomass，rootmorphology，residual soil nutrientcontent，nitrogen useefficiency，solution nitrogencontent，and discuss the effects of biochar on growth and nitrogen utilization ofcrops in twosoils.The results showed that the biochar amendments significantly reduced the aboveground and underground biomass of Pakchoi planted in fluvo-aquicsoil，with a decrease of 59.1%～77.2%，70.6%～80.6%，but significantlyincreased the aboveground and underground biomass of Pakchoi planted in redsoil，with an increase of 35.7%～69.0%， 63.0%～77.1%.In addition，the biochar had a significant effect on its root morphology.Biochar application reduced the root length and the root surface area of Pakchoi by 11.5%～ 30.1% and 45.6%～ 55.9% in fluvo-aquic soil.Theratio of root to shoot showed a trend of increasing firstly and then decreasing，the biochar amendments in red soil had nosignificant effect on the root length ofPakchoi，which increased the root surface area by 47.5% and56.7%，decreased the ratio of root toshoot.The results indicated that the biochar application promoted the Pakchoi root growth in red soil；and inhibited the Pakchoi root growth in fluvo-aquic soil.The biochar amendments decreased the nitrogen absorption efficiency，nitrogen partial productivity of Pakchoi by 64.7%～73.5%，65.1%～ 79.3% in fluvo-aquic soil.And biochar amendmentsincreased the nitrogen absorption efficiency，and the nitrogen partial productivity of Pakchoi by 44.7%～59.6%，and32.0%～63.2% in redsoil.At the sametime，biochar application significantly reduced the nitrate content of Pakchoi by 40.9%～84.6% and 18.8%～75.0%，respectively.Biochar application can promote the Pakchoigrowth，increase itsyield，reduce the nitrogen residue in redsoil，and improve the nitrogen utilizationefficiency.It has good ecologicalbenefits.But biochar applation in fluvo-aquic soil can inhibit Pakchoi root development，reducing itsyield，and nitrogen fertilizer utilizationefficiency，the effective and safe application of biochar in fluvo -aquic soil still needs further exploration.