Using the Hydrothermal process to reduce the volume of the MSW which is mostly organic component and to utilize the solid powder resulted as coal-like solid fuel will benefit not only in solving the MSW problem but also reducing the coal consumption in the power plant. In this study, the hydrothermal processes were done using a laboratory scale apparatus with MSW components as the samples. The process conditions comprised temperature, solid load, and holding time. Four typical components were used as representative pseudo-components of organic and plastic fraction of municipal solid waste. In this study, the experiments were done at various temperatures, 180 oC, 200 oC, and 220 oC inside an experimental autoclave. The results of the experiments show that the process time, the water amount and the temperature which are used in hydrothermal process, affect the proximate and ultimate compositions. The moisture and fixed carbon content decrease and the volatile matter increases, so that the MSW’s calorific value increases. Based on the experiments, the optimum hydrothermal process parameters are feed to water ratio of 1/1 (250g/250ml), temperature of 180 oC, and holding time of 90 min. It also can be concluded that hydrothermal process can be applied to MSW to produce solid fuel.