Nitrogen (N) is an important limiting factor affecting net primary productivity in terrestrial ecosystems. Consequently, increasing N deposition would profoundly affect litter chemical properties and biomass production, which further affect litter nutrient inputs to soil. However, how long-term N addition influence twig litter nutrients and biomass production is poorly understood. This is especially true for the alpine shrublands, which are important component of terrestrial ecosystems. To fill this gap, we examined N effects on the twig litter stoichiometric properties and nutrient return in an alpine shrubland dominated by Sibiraea angustata of western Sichuan Plateau, China. This shrubland received four levels of N input (N₀, control; N₂₀, 20; N₅₀, 50; N₁₀₀, 100 kg hm^-2 a^-1) during four growing seasons from 2012 to 2015. Our results showed that N addition did not significantly affect total C and N concentrations in the twig litter (P>0.05), but did significantly affect total P, lignin, and cellulose concentrations (P<0.05). The ratios of C/N and N/P did not change significantly after N addition, while the ratios of lignin/N, C/P and C/N/P significantly decreased in the third, first and fourth, and first year of N addition, respectively. Cumulative production of the twig litter biomass, C, N, P, lignin and cellulose (g m^-2 a^-1) from 2012 to 2015 showed a significant quadratic response to increasing N (P<0.05), with the largest value observed for N₅₀ treatment. Our results indicated that the effects of N on the twig litter stoichiometric properties showed a largely annual variation, and appropriate N input promoted carbon and nutrients return to soil by increasing twig litter biomass rather than altering litter chemistry.