Soil pH value is the most important soil property. It can not only directly affect the growth of crops, but is also involved in altering other soil properties. Our objective was to determine the difference in soil pH values between Picea asperata and Abies faxoniana stands and its mechanism. We used the seedlings of Picea asperata and Abies faxoniana, the widely distributed and important species in subalpine coniferous forests of Sichuan, China, as materials with which to conduct the experiment. We measured soil pH values of different soil layers, calculated the cumulative H⁺ input through nutrient uptake and storage in biomass, and forest floor accumulation, and analyzed the litter quality. The results showed that the pH value of A. faxoniana soil was greater than that of P. asperata. The soil pH value was significantly positively related to the calculated cumulative H⁺ input through forest floor accumulation, and negatively related to the first principal component scores of different plots. Thus, soil pH value was significantly positively related to the ratio of lignin/N, C/N, C/P, and total concentration of Ca, and negatively related to total concentrations of N and P in leaf litter. The results suggested that the difference in the soil pH values between P. asperata and A. faxoniana was related to the forest floor accumulation and the leaf litter quality, i.e., the mass, decomposition, and nutrient-restitution of leaf litter.