Flame-retardant plant fiber and flame-retardant paper

The invention relates to the field of a flame-retardant material, and especially relates to flame-retardant plant fiber and a piece of flame-retardant paper. The flame-retardant plant fiber comprises plant fiber slurry and a fire retardant; a preparation method of the flame-retardant plant fiber comprises the following steps: a magnesium chloride solution whose concentration is 0.8-1.4mol/L is added into a reactor with heating and stirring, the temperature is controlled at 50-70 DEG C, the plant fiber pulp and an ultrafine filling material are added, stirring is carried out for 20-40 minutes, ammoniacal liquor whose mass fraction is 2.0-2.5% is added, stirring is carried out for 10-30 minutes, the plant fiber pulp is filtered and washed with clear water, and the flame-retardant plant fiber is obtained. The flame-retardant paper which is made from the flame-retardant plant fiber has the advantages of good flame retardation effects, low influence on physical strength of paper, low production cost, and environment protection.