Abstract: Against the backdrop of green agricultural development and chemical fertilizer reduction and efficiency improvement, it is of great significance for promoting regional sustainable agricultural development to systematically evaluate the chemical fertilizer substitution potential of crop straw and livestock manure, as well as land carrying capacity. Based on statistical data of Anhui Province from 2014 to 2023, the study area was divided into three regions: Northern, Central, and Southern Anhui. The resource quantities of straw from major grain crops and livestock manure were estimated using the straw-to-grain ratio method and excretion coefficient method, and their theoretical potential for chemical fertilizer substitution was analyzed. A land carrying capacity model based on nitrogen balance was constructed. The results showed that the total amount of agricultural waste in Anhui Province generally exhibited an increasing trend over the past decade, demonstrating considerable nutrient supply potential. In 2023, the theoretical contents of nitrogen (N), phosphorus pentoxide (P₂O₅), and potassium oxide (K₂O) in crop straw across the province were 3.942×10⁵, 7.98×10⁴, and 6.505×10⁵ tons, respectively, while those in livestock manure were 4.846×10⁵, 3.751×10⁵, and 4.304 ×10⁵ tons, respectively. Nutrient resources exhibited a pronounced spatial distribution pattern, with Northern Anhui accounting for approximately 60% of the province’s total crop straw and manure resources. Under idealized return-to-field scenarios, crop straw showed the greatest potential for K₂O fertilizer substitution, whereas livestock manure demonstrated a clear advantage in P₂O₅ fertilizer substitution. The land carrying capacity assessment revealed that the overall scale of livestock and poultry breeding in Anhui Province remained below the theoretical maximum land carrying capacity, although Huangshan City and Xuancheng City exhibited varying degrees of theoretical overload. These findings provide a scientific basis for promoting the resource utilization of agricultural waste, implementing differentiated regional management strategies, and advancing the coordinated development of crop–livestock systems in Anhui Province.