Sisal fiber cellulose microcrystallines (SFCM) was coated with a fully renewable flame-retardant coatings consisted of cationic chitosan (CH) and anionic phytic acid (PA) via layer-by-layer (LbL) assembly. The structure and properties of the formed microcrystallite composite were characterized by Zeta potential, TGA, FESEM, VFT, and MCC methods. Zeta potential and FESEM results show that the surface charge of the coated cellulose microcrystallites reversed due to the adsorption of polyelectrolyte during multilayer deposition process. TG analysis show that the initial decomposition temperature of the composites decreased from 299℃ to 257℃ and the residues increased from 5.41% up to 37.34% with the increase of CH/PA film layers. Examination of SFCM(CH/PA)₅ residues by FESEM revealed that the distinct fiber structure have been preserved and insignificant fiber shrinkage was observed.Vertical combustion testing (VFT)results show that for SFCM(CH/PA)_{5 ,} in comparison with the plain SFCM, the afterflame time is drops from 150 s down to 39 s; the pkHRR and total heat release (HR)exhibit great reduction of 70.6% and 79.2% respectively. These results demonstrate that the CH/PA coating has obviously improved the flame retardant performance of SFCM.