Abstract: The purpose of this study was to utilize the biomass from Ulva pertusa kjellman to produce biodegradable boards for substituting the oil-based plastic materials. The experiment involved refining the Ulva pertusa kjellman in water, and then using thermostat in the same condition to defibrate fibers. In this process, fiber tip was changed to be fine cellulose. In the next process the materials were pressed for linking cellulose to be a biomass board. Finally, the biomass board was dehydrated and combined by heat conduction dryness. Technical evaluation of the resulting biodegradable board shows a rupture stress of 131 MPa, which is four times stronger compared with the polystyrene plastic material used in food container presently. Therefore, the use of biomass board as a substitute for the oil-based plastic materials as food packing container, culture pan, mulch film and so on is technically possible.