The increasing municipal solid waste can cause environmental pollution problems. The organic fraction is the largest component of municipal solid waste, reaching 75%, mostly around 61% from kitchen waste. One method to reduce the impact of pollution from municipal waste by processing it into Refused Derived Fuel (RDF) with bio-drying method. The combination of osmosis process treatment by soaking organic waste in a NaCl solution before the biodrying process can speed up the drying process. Immersion was carried out for four days. Every day the water content analysis was carried out by weighing. This paper provides an effect evaluation of 5%, 15%, and 25% NaCl solution as osmosis media on reducing the organic waste's water content. The organic waste are simulated using tomatoes, water spinach, cooked rice, and tofu. The higher the NaCl concentration (maximum 25% studied), the greater the ability to reduce the water content, 25% in water spinach and 40% in tomatoes. In tofu and cooked rice, soaking in NaCl solution increased the water content by 20% and 100%, respectively.