Due to local economic development, the Central Shaanxi reach of the Wei River suffers from serious water contamination, which is restricting sustainable development in this area. Therefore, it is desirous to study the water environmental capacity here in order to improve water quality. In this paper we chose chemical oxygen demand (COD) as the index, which reflects the organic contamination. After the unit division and parameter design, we used one-dimensional steady-state model to calculate the water environmental capacity of the Central Shaanxi reach of the Wei River. The results show that the water environmental capacity of the Central Shaanxi reach of the Wei River varies with different conditions, for instance, with the months, as well as with the seasons. We have determined that seasonal pollutant load distribution and total quantity control could help us utilize the water resource more effectively.