Biochar is known to be a good soil amendment to improve soil physical and biochemical characteristics, to increase crop yield, and to mitigate greenhouse gas emissions from soils. In this study, five addition levels of apple tree branches-derived biochar (0, 20, 40, 60, 80 t·hm~(-2)) were used in field plot test. The effects of biochar on soil temperature, soil aggregates, NO_3~--N, NH_4~+-N, microbial biomass carbon and greenhouse gas fluxes were investigated during the whole pepper growth season. The results showed that biochar amendment increased the temperature moderation capability of soil and increased the content of soil macro-aggregates, especially the content of aggregates with sizes >5 mm, 5-2 mm and 1-0.5 mm. As compared with the control, the contents of NO_3~--N, NH_4~+-N and microbial biomass carbon increased by 4.9%-33.9%, 9.1%-41.1% and 11.8%-38.5% with the increase of biochar content respectively. Biochar amendment increased CO_2 emissions and CH_4 uptake by 6.73%-23.35% and 3.62%-14.17%, respectively. N_2O emissions and global warming potential (GWP) decreased at biochar levels of 20 and 40 t·hm~(-2) and increased when the biochar levels were 60 and 80 t·hm~(-2) as compared with the control. The results suggested that as a soil conditioner, biochar improved soil quality, soil fertility and function of agriculture soil on carbon sequestion and decreased emission cut. In addition, the choice of biochar level is very important.