Abstract: Inorganic materials such as sodium silicate and aluminum sulfate can be used as additives to improve mechanical and fire resistance performances of plant fiberbased ultra low density material (ULDM) during its making process using the liquid frothing approach. Following process was used to make sample mats: after fiberization in a refiner, adding resin and surface active agent in the pulp solution, then adding sodium silicate and aluminum sulfate, well mixing the solution; after solution frothing, mat forming and drying, a plant fiberbased ultra low density mat was made. Compared with 0 inorganic additive, using 40% sodium silicate and corresponding amount of aluminum sulfate could increase internal bonding strength of the ULDM from 0.1 MPa to 10 MPa, MOE from 12.4 MPa to 87.3 MPa; MOR from 0.2 MPa to 7.3 MPa and compressive strength (at 10% strain) was ranging from 0.2 MPa to 3.7 MPa. This also can reinforce fire resistance performance and oxygen index reach a higher level of 42%. No significant weight loss and exothermic decomposition could be observed below 700 ℃.