This study investigated the effectiveness of sugarcane leaves return to the nitrogen demand of sugarcane and soil nitrogen replenishing, providing a scientific basis for the utilization of sugarcane leaf return as fertilizer. The field experiments were conducted using the sugarcane variety Guitang42, with three treatments of 15N-labeled sugarcane leaves: 100% applied at the bottom of the furrow (T1), 50% at the bottom + 50% on the surface of the furrow (T2), and 100% on the surface of the furrow (T3). The effects of these treatments on sugarcane yield, nitrogen uptake by sugarcane and nitrogen replenishment in soil from returned sugarcane leaves were analyzed . Results showed that T1 had the fastest and most abundant emergence in plant sugarcane season, with the highest number of stalks and yield in two crops. In the three treatments, the nitrogen derived from returned sugarcane leaves accounted for 1.24%–1.41% and 1.45%–1.55% of total nitrogen in plant sugarcane and first ratoon sugarcane, respectively, with amounts of 2.69–3.28 kg/hm2 and 2.55–3.03kg/hm2, and T1 had the highest absorption in both crops. After first ratoon sugarcane harvest,the nitrogen contribution rates of returned leaves to the 0–20 cm and 20–40 cm soil layers were 1.27%–1.41% and 0.01%–0.71%, respectively, with amounts of 27.98–31.86 kg/hm2 and 0.11–5.55 kg/hm2, respectively. T3 and T1 contributed more nitrogen to the 0–20 cm and 20–40 cm soil layers, respectively. The utilization, residual, and loss rates of nitrogen from returned sugarcane leaves were 5.42%–6.61%, 78.17%–80.68%, and 12.71%–16.41% in plant season, respectively, and 5.14%–6.10%, 64.39%–67.53%, and 7.05%–8.64% in first ratoon season.T1 had the highest utilization and residual rates in two crops, while T3 had the highest loss rate. Overall, the direct contribution of returned sugarcane leaves to the nitrogen demand of sugarcane is very limited, while its supplementation to soil nitrogen is relatively substantial. Moreover, T1 achieved higher stalk yields and utilized more nitrogen from returned sugarcane leaves.