The LFP-86 fire retardant is a light yellow transparent, liquor which contains N and P. Theresult obtained from experiments on treating wood of Fraxinus mandshurica indicates that the oxygen index of LFP-86 fire retardant is 57 and the retardancy of LFP-86 treated wood meets class I according to JIS D 1201, When the intake of LFP-86 fire retardant is over 60kg/m,3,and temperature up to 1000℃, the rate of weightloss will be about20% after bur ning 3 rains LFP-86 fire retardant has no ability to defend fungi and ter mites attack In impact bending,bonding strengthand hygrosscopicity resistance, treated woods are lower than untreated woods. LFP-86 has no effects on paintability and corrosivity. There are indications that LFP-86 may be used as a fire retardant for indoor timber and woodcrafts.