This study collected 12 typical soil samples from the Robinia pseudoacacia forest on the north-south strip of the Loess Plateau to understand the ecological stoichiometric characteristics of its soil carbon (C), nitrogen (N), and phosphorus (P). The contents of soil organic carbon (SOC), total N, and total P were determined, and their ecological stoichiometric characteristics were analyzed. The results showed that the content of SOC, total N, and total P in the Robinia pseudoacacia forest decreased with a decrease in precipitation, including the spatial variation in the SOC and total N. The soil C, N, P, and their ecological stoichiometries were significantly positively correlated with precipitation (P < 0.05), and there was a significantly positive correlation between the total N, C:P, N:P, and soil water content (P < 0.05).