【Objective】Soil nitrogen is an important indicator of soil fertility of farmland, and also an important component of the nitrogen pool in the terrestrial ecosystem. It is of great significance to exploration of nitrogen circulation in the terrestrial ecosystem and its effect on the environment to study dynamics of the soil nitrogen deposit in farmland. So far, much has been reported both at home and abroad on soil nitrogen deposits on a varying scale, but most of the studies on deposit of total nitrogen in farmland on a regional scale focus on static status of nitrogen deposit of a certain time period, and little has been done on dynamics of soil nitrogen deposit in farmland on a provincial scale based on large volumes of data gathered from huge numbers of sampling sites and spatial database relatively high in accuracy. As a result, it is still very hard for the country to work out proper measures for management of farmland nitrogen on a regional scale in line with variation trend of soil nitrogen content. 【Method】In this research project, with the aid of the ArcGIS 10.2 software and the inverse distance weighting interpolation (IDW) method, based on the data of topsoil attributes collected from 2 021 sample soil profiles during the second soil survey in 1982 and 29 945 sampling sites in extrapolation of soil surfaces of soil testing and fertilizer recommendation in 2008, and the data of average annual nitrogen application rate fertilizer, average annual temperature and average annual precipitation of the past 30 years of Fujian Province, a 1:50,000 high accuracy mapping scaled farmland soil total nitrogen and relevant attribute database of the province was established. This database, containing a total of 462 630 patches, was used to study dynamic changes in soil total nitrogen density and storage in the farmland of the province in the past 30 years.【Result】Results show that the soil total nitrogen density and storage in the farmland of Fujian Province was 0.258 kg m^-2 and 4.26 Tg respectively, in 1982, and rose to 0.262 kg m^-2 and 4.39 Tg, respectively, in 2008, which indicates that soil total nitrogen in the farmland of the province was on a rising or enriching trend. Analysis on a prefectural-level city scale shows that the soil total nitrogen density rose the most or by 0.036 kg m^-2 in Longyan City, but dropped the most or by 0.041 kg m^-2 in Xiamen City. In terms of soil type, it rose the most or by more than 0.015 kg m^-2 in soils of the group of fluvo-aquic soil and the sub-type of gleyed paddy soil, and dropped the most or by more than 0.015 kg m^-2 in soils of the group of calcareous soil and the sub-types of submergenic paddy soil. It is quite clear that as a whole, in the past 30 years, the soil total nitrogen in the farmland of the province varied sharply in density spatially.【Conclusion】Consequently, the province should work out site-specific optimal nitrogen fertilizer management programs for its management of farmland soil nitrogen in future in the light of soil types of the farmland and the degree of nitrogen enrichment in farmland on a prefecture-level city scale. The programs are essential to the control of agricultural non-point source N pollution, protection of eco-environment and realization of agricultural sustainable development.