This study aimed to assess fifteen indigenous microorganisms (IMO) ability to decompose the rice straw, sugarcane bagasse, coco peat, sawdust, and rice husk as organic materials collected from different farming systems in Soc Trang province, Vietnam. Microbial density capable for cellulose decomposition was determined by the plate counting method on agar medium containing 1% carboxymethylcellulose. Cellulose degradation capacity of IMO was qualified by Congo red method with determination of a halo zone diameter. Finally, the decomposition capacity of IMO for organic materials was determined by the mass loss method after 30 days of inoculation under laboratory conditions. The results showed that the density of cellulose decomposer in IMO was around 10⁵ CFU/g and all 15 IMOs had halo zone diameters varying between 3.38 – 8.63 cm. Results of the decomposition experiment for five different organic materials under the laboratory conditions revealed that percentage of decomposition of rice straw material was ranged between 52.2 – 57.9%.  The percentage of sugarcane bagasse decomposition  varied from 19.03 to 47.72% while the values for the control treatments without IMO inoculation of these two materials were 20.39% and 11.81%, respectively. However, for other materials including coco peat, sawdust and rice husk, all fifteen IMO₂ exhibited very low capacity in decomposition and there was no significant difference between the treatments with and without IMO₂ inoculation regarding to the decomposition rate of the organic materials. The results of this study indicated that IMO₂ can be used to enhance the decomposition  rate of some agricultural waste products in the composting process.