【Objective】The problems caused by excessive nitrogen(N) application in agriculture has been of growing concern, but the soil mineral N level and its effect on straw decomposition after long-term N application remain unclear. 【 Method】 We used a fluvo-aquic soil treated for 14 years(2005-2018) with N at the rates of 0(N0), 150(N1), 190(N2), 230(N3) and 270(N4) kg·hm^-2·a^-1, and conducted a 50-day laboratory incubation experiment with and without straw addition. Soil CO₂ emission was determined during the incubation, soil mineral N(nitrate and ammonium nitrogen), dissolved organic carbon(DOC), microbial biomass carbon(MBC) were measure before and after the incubation, and the bacterial community structure was determined using amplicon sequencing of the 16S rRNA genes. 【 Result】 Results show that soil mineral N content and straw decomposition efficiency increased with increasing N application rates and the bacterial community composition was significantly(P<0.05) influenced by N application rates. The network analysis revealed that the co-occurrence pattern among species within the bacterial community during straw decomposition changed with the N application level, and the negative association among bacterial communities was strengthened under a high N application level. At the same time, the dominant position of Proteobacteria was weakened and that of Acidobacteria was enhanced.【 Conclusion】 The soil inorganic nitrogen content increased with the increase of long-term nitrogen application level, resulting in changing in soil bacterial community structure. Thus soil bacterial community structure of different long-term nitrogen application played different roles in the process of straw degradation, which was manifested as the increase of straw degradation with the increase of nitrogen application level. The relationship among soil mineral N content, bacterial community structure and species changed with the difference of long-term N application level. The results of this study provide guidelines for the use of straws to amend soils under N application.