Abstract: We evaluated the carbon metabolism characteristics of soil microbial communities under half-reduced N fertilization combined with organic fertilizer in the oat field. The aim was to investigate the possibility of the replacement of partial N by organic fertilizer from the perspective of soil microbial functional diversity. There were five treatments in the experiment: no fertilizer CK, conventional nitrogen N1 (pure N 90 kg·hm^-2), nitrogen fertilizer halved N2 (pure N 45 kg·hm^-2), and nitrogen fertilizer halved combined with organic fertilizer N2O1 and N2O2 (O1 contains a total N of 90 kg·hm^-2 and O2 contains a total N of 45 kg·hm^-2). The Biolog-ECO method was used to evaluate the metabolism characteristics of soil microbial communities on carbohydrates, amino acids, amines, carboxylic acids, polymers, and others. The results showed that N fertilizer halved combined with organic fertilizer changed the metabolic preferences of soil microbial communities on carbohydrates, amino acids, carboxylic acids and polymers in the oat field. After N fertilizer halved, there was a significant increase of the utilization on the six types of carbon sources for soil microbial communities with the increasing organic fertilizer application. Principal component analysis showed that amino acids and amines were the main carbon sources which induced the metabolism characteristic differences of soil microbial community among different fertilization regimes. After N fertilizer halved, richness and evenness of soil microbial communities were increased with the increasing organic fertilizer application. After N fertilizer halved, when the amount of organic fertilizer equaling total N of 90 kg·hm^-2, oat yield was increased by the changes of soil microbial functional diversity. Therefore, N fertilizer reduction and organic fertilizer substitution was an effective measure to improve soil microbial functional diversity in oat fields.