Abstract: Background and Objective: Rice residues such as rice straw and rice husks are very abundant in Indonesia. However, until now the remaining rice harvest has not been utilized properly. Whereas, the rest of the rice harvest can be used as organic material that can increase agricultural productivity by making compost. Therefore, this study aims to determine the most effective decomposer to be used as an acceleration in composting the remaining rice harvest. Materials and Methods: The method used in this study was to compare 4 decomposers namely PGPR, EM 4, Semanggi and Garuda in composting rice straw and rice husks. After that, the compost was analyzed for its chemical properties and bacterial diversity. Results: The results of the bacterial analysis found 26 bacteria which 4 were gram-negative with genera Pseudomonas and 22 were gram-positive, with 9 genera of Coryneform/Streptomyces and 12 genera of Clostridium. From the chemical analysis, it was found that there were differences in decomposition activity during composting due to differences in compost materials, as indicated by the observed physical and chemical parameters. Conclusion: The highest production of C-organic was straw compost with Garuda decomposer at 39.47%, also in straw Garuda decomposer compost were found 4 different genera of bacteria which mean it has a good of diversity microorganism.