The effect of milling time on the microstructure of chitosan nanopowder had been investigated. This study fabricated chitosan nanopowder viaball millingat different milling time.The milling time usedwere 0, 60, 180 and 360 minutes, indicated by CHO, CH60, CH180 and CH360, respectively. From the SEM results, the milling time not only resulted in the homogenous dispersion but also the reduction ofparticle clustering and the reduction of distances between the particles. The optimalgrain and crystallite size of CH180 is 8.5 nm and 20.1 nm, respectively. The chitosan nanopowder showed thatthe milling time does affect the crystallitesize. The average crystallitesize of chitosan nanopowder is 20nm. The dielectricconstantand loss valuesdecrease with the frequency and increase with the milling time. Thus, the effect of milling time on microstructures and dielectric properties of chitosan nanopowder could increasethe internal structure of the granules and applied to synthesis the solid electrolyte.