With zinc acetate used as raw material and polyethylene glycol employed as dispersant, ultrafine ZnO flower-like powder was successfully synthesized by hydrothermal method using NaOH and NH3·H2O as precipitants. The influences of the precipitants on the morphology of the ZnO powder were discussed. The as-synthesized ZnO flower-like powder was composed of lots of microrods with hexagon figure. The ZnO flower-like structures synthesized using NaOH were more regular and uniform than that obtained using NH3·H2O. The ZnO flower-like powder was hexagonal wurtzite structure with high purity. The exciton absorptions of the two ZnO flower-like powder both appeared at 300 nm in UV-VIS spectrum.