An isocyanate resin and an FRA retardant developed by the authors were used to manufacture fire-retardant low density fiberboards at 0.40 g/cm3.Four technological factors,including resin consumption, hot-pressing temperature, pressing time and fire-retardant consumption were investigated and the performance of the fiberboards was evaluated.The results showed that the FRA retardant consumption could improve the fire-proof property of the fiberboards.The performance of the fiberboards made under optimal conditions could meet the specifications of industrial standard LY/T 1718-2007 for low density fiberboard.