【Objective】 Investigating the fate of fertilizer nitrogen in a two-season crop system under different straw returning methods can provide an important basis for nitrogen management under black soil protection.【Method】 This study conducted a ¹⁵N micro-plot experiment in 2020-2021 at Lishu County of Jilin Province using the ¹⁵N tracer technique. Three straw-returning methods were set up:no straw returning(CK), straw deep tillage returning(DTS) and straw mulching with no tillage(NTS). Under each method, two nitrogen levels were set:180 kg·hm^-2(N1) and 270 kg·hm^-2(N2). 【Result】 At maturity stage, 38.0%-46.8% and 12.9%-18.6% of plant nitrogen in the current season and the second season were derived from ¹⁵N labeled nitrogen fertilizer, respectively, and fertilizer nitrogen was mainly distributed in grains (59.8%-68.5% in the current season and 59.3%-79.6% in the second season). The utilization, residual and loss rates of fertilizer nitrogen in the current season were 32.4%-43.9%, 32.8%-51.4% and 13.2%-32.7%, respectively. The NTS combined with an appropriate amount of nitrogen fertilizer (180 kg·hm^-2) significantly increased the utilization rate of fertilizer nitrogen by 29.5%, while DTS significantly increased the residual rate of fertilizer nitrogen in soil by 18.6%. Also, the utilization and loss rates of fertilizer nitrogen in the second season were 8.5%-14.9% and 5.1%-14.6%, respectively. The cumulative utilization, residual and loss rates were 40.9%-58.8%, 10.4%-26.4% and 18.4%-47.3%, respectively. Compared with CK, NTS treatment significantly increased fertilizer nitrogen utilization efficiency by 18.3% (N1) and 45.9% (N2) in the second season, while the DTS treatment significantly increased fertilizer nitrogen utilization efficiency in the second season by 42.3% under N2. For the total fate of fertilizer nitrogen in two crops, compared with CK, NTS treatment significantly increased the cumulative utilization efficiency of fertilizer nitrogen by 26.4% (N1) and 21.8% (N2), while DTS treatment significantly increased the total residual rate of fertilizer nitrogen by 64.0% (N1) and 72.9% (N2). In addition, the NTS and DTS treatments significantly reduced the total losses of fertilizer nitrogen. Compared with N2, the N1 treatment significantly increased the utilization and residual rates of fertilizer nitrogen and reduced the loss rate of fertilizer nitrogen in two seasons.【Conclusion】 Straw mulching combined with an appropriate amount of nitrogen fertilizer is beneficial to improve fertilizer use efficiency while straw deep plowing is more conducive for the maintenance of fertilizer nitrogen in the soil, especially under high nitrogen application rate, and increases the use efficiency by next crop. Both straw mulching and straw deep plowing could significantly reduce nitrogen loss.