Nitrogen is one of the main nutrient limiting factors in farmland soils. The study on the response of soil nitrogen to temperature and precipitation changes under the scenario of global climate change, will have a great significance to evaluate the ecological effects of climate change on agriculture. To investigate the effect of warming and reduced precipitation on soil nitrogen, field experiments with simulation warming using infrared lamp radiation and artificial reduction of precipitation were conducted in the 2015-2016 winter-wheat and soybean growing season. The experimental treatments included the control (CK), diurnal warming (T, about enhanced 2 ℃), 30% reduced precipitation (P), and the combined treatment (TP, warming about 2 ℃ plus 30% reduced precipitation). The results showed that in the winter wheat-growing season, compared to CK, T, P and TP treatments significantly reduced soil total nitrogen in the turning green stage, and significantly increased soil total nitrogen in the maturity stage. T and TP treatments significantly reduced soil total nitrogen in the elongation stage. T, P and TP treatments significantly reduced soil NH_4~+-N in the booting-heading stage. P and TP treatments significantly increased soil NO_3~--N in the turning green - grain filling stage, and T treatment significantly increased soil NO_3~--N in the elongation - heading stage. In the soybean-growing season, compared to CK, T, P and TP treatments had no significant effect on soil total nitrogen. T treatment significantly increased soil NH_4~+-N by 10.0% (P=0.038) in the grain-filling stage. T and P treatments significantly reduced the soil NO_3~--N by 27.4% (P=0.011) and 27.1% (P=0.009) in the podding stage, respectively. T, P and TP treatments significantly increased soil NO_3~--N by 46.6% (P=0.007), 41.3% (P=0.014) and 56.3% (P=0.003) in the grain-filling stage, respectively. Our findings suggest that warming and reduced precipitation may alter soil nitrogen content of farmland, and there is an more obvious effect on soil nitrogen in winter-wheat farmland than in soybean farmland.