Due to large-scale commercial logging and prolonged anthropogenic disturbances over the past decades, large tropical secondary forests have been converted into rubber plantations, which have substantial impacts on soil bacterial community via altering soil properties. However, how forest conversion affect soil bacterial community composition and diversity are still poorly understood. To address this, we compared the soil bacterial communities and physicochemical properties between typical secondary forests (SF) and rubber plantations (RP) in Hainan Island. The results showed that SF exhibited higher soil organic matter, total nitrogen, total carbon and pH compared to RP, particularly in the 0-10 cm layer. Besides, the soil bulk density in SF was lower than that in RP. The bacterial community composition and microbial networks were significantly varied between SF and RP. The dominant soil bacterial phyla in SF were Proteobacteria (27.37%–28.66%), followed by Acidobacteria (18.97%–19.82%), while Chloroflexi prevailed in RP (27.89%–28.45%), followed by Acidobacteria (20.93%–24.38%). Furthermore, SF exhibited more complex microbial networks owing to its higher edges, degree and links compared to RP. Meanwhile, bacterial community assembly in SF was primarily governed by deterministic processes, while stochastic processes dominated RP. The soil bacterial α-diversity in SF was higher than that in RP, which was primarily dominated by pH. Our findings demonstrate that converting secondary forests to rubber plantations does not favor soil microbial diversity and stability, as it decreases soil pH, which suggests that sustainable management strategies should prevent soil acidification in rubber plantations.