The crystallization of zinc oxide from sodium zincate solution is the key step in the process for treating zinc oxide mineral ores and residues by NaOH method. The crystallization kinetics including nucleation, growth and aggregation was investigated in a batch crystallizer. It was found that zinc hydroxide could be converted into zinc oxide under hydrothermal conditions without calcinations. Effects of temperature, seed, supersaturation and agitation speed on the crystallization were studied. The main structure of zincate changed with varied temperature. Zinc oxide particles were spherical particles formed by agglomeration of zinc oxide nanorods. The growth rate, the nucleation rate and the aggregation kernel were calculated by moments analysis based on the particle size distribution. The volume growth mechanism and linear growth mechanism of zinc oxide were controlled by diffusion process and surface reaction. In batch crystallization, the nucleation rate decreased with the increase of suspension density but increased with the increase of agitation rate. The reaction time had the most significant effect on the agglomeration factor. The agglomeration between zinc oxide particles could be improved by increasing the particle collision frequency.