Cellulose was fibrillated by high pressure water. Dispersion of produced cellulose nanofiber (CNF) didn’t have almost no deterioration of crystallinity and was spray-dried to be a fine powder and compounded with polylactic acid (PLA) and additives. The fine powder of CNF was dispersed in PLA with strong shearing or the additive with an affinity for CNF and PLA. Non-reactive additive improved the dispersibility of CNF in PLA, but could not improve physical and thermal properties simultaneously such as flexural strength, IZOD impact strength, and deflection temperature under load and so on. But polyfunctionalized reactive additive could improve these properties difficult to make compatible. In comparison with a conventional method to bring polarity close to resin, this method, which is simple, inexpensive and versatile, can be expected to have superiority in properties because reactive additive crosslinks resin and nanofiber.