Rhizosphere soil organic nitrogen (SON) fraction play an important role in soil nutrients and crop nitrogen (N) nutrition. This study was based on a long-term (37 years) located fertilization experimental field, including four fertilization treatments: without fertilizer input as a control (CK), chemical fertilizer alone (CF), rice straw residue and chemical fertilizer (RF), and 30% organic manure and 70% chemical fertilizer (OM). At the maturity stage of late rice, the rhizosphere soil basic physiochemical properties, microbial biomass N (MBN) and SON fractions, including amino acid N, amino sugar N, ammonia N, hydrolysable unknown N, non-hydrolysable N in barley-double cropping rice field were determined. The results indicated that RF and OM significantly increased the contents of soil organic carbon (SOC), total N, ammonium N and nitrate N in rhizosphere soil compared to CK. Soil MBN content was significantly increased by 19.8% and 30.7% under RF and OM, respectively, compared to CK. Rhizosphere soil acid hydrolyzable N was the main component of soil total N, accounting for 59.61%–72.06% of total N. The content of acid hydrolyzable N in rhizosphere soil was in order of OM>RF>CF>CK. Soil amino sugar N, amino acid N and hydrolysable unknown N contents were found significantly highest under OM, increased by 139.3%, 47.9% and 110.0%, respectively, compared to CK. Soil ammonia N content was significantly highest under RF, with an increase of 69.9% over CK. SOC, total N, ammonium N and nitrate N contents all showed a significantly positive correlation with soil amino acid N, amino sugar N, hydrolysable unknown N and MBN contents. Therefore, the application of rice straw or organic manure and chemical fertilizer is an effective practice for improving soil fertility, which can effectively increase the capacity of rhizosphere soil N supply in barley-double cropping rice field.