An incubation experiment was conducted to investigate the effects of corn straw and biochar on acidify and exchangeable capacity in tropical latosol originated from granite in order to support the theoretical basis for improving quality of latosol in tropical region. Biochar (B), corn straw (CS) and biochar + corn straw (BCS) were applied into soil, respectively, and no organic material was arranged as control (CK). Amending B, S and BS could significantly increase pH, CEC, ion exchange capacity and base saturation percentage, but highly decreased soil exchangeable acid, especially for exchangeable aluminum of exchangeable acid, which suggest that B and S can effectively reduce soil acidify, increase exchangeable capacity in tropical region. The improvement effects of organic materials was in order as CS, BCS and B.