Four gradients of simulated acid rain treatment[pH 3.0, 3.5, 4.0 and CK (lake water)] were designed to determine the effects of simulated rain on soil carbon stabilization and the carbon management index (CMI) in three subtropical forests at different successional stages. The stages are, a young pine forest (PF), a transitional mixed conifer and broadleaf forest (MF), and an old grow-growth broadleaved forest (BF) at the Dinghushan Nature Reserve. The soil organic carbon (SOC), readily oxidation organic carbon (ROC), particulate organic carbon (POC), microbial biomass carbon (MBC), dissolved organic carbon (DOC), and soil properties were analyzed. The results showed that the SOC, ROC, and POC contents increased with acid treatment. However, simulated acid rain restrained the activity of microorganism while the SMBC content showed the opposite trend. The analysis showed that ROC₃₃₃ and POC with SOC had highly significant correlations, with correlation coefficients of 0.853 and 0.846 respectively. Our results also indicated a significant correlation between other labile fractions and the SOC. The value of L and LI decreased with the progressive succession of forests while the rangeability of L and LI showed the same trend. It's indicated the proportion of labile portion to non-labile portion decreased. The results also showed CPI and CMI increased with the progressive succession of forests and, thus, the BF soil pool was more stable. That's due to BF soil has higher C sequestration and lower lability than MF and PF forests, so the carbon is easily to sequestrate and more stable if the carbon lability index decreased. Moreover, the LI was more sensitive than the carbon cool index (CPI) was. From the variation of indicators of the three forests, we can conclude that the response sensitivity of acid rain showed an increasing trend with the progressive succession of forests. All the parameters investigated showed the following order of decreasing sensitivity:CMI > R₃₃₃ > POC > SMBC > R₁₆₇ > R₃₃ > LI > DOC > CPI > SOC.