The crystallization of monosodium aluminate hydrate (MAH) from sodium aluminate solution is the key step in the hydro-chemical process for treating Bayer red mud. The nucleation, growth and aggregation kinetics of MAH from unseeded sodium aluminate solution with low supersaturation was studied. It was found that the increase of temperature or the decrease of initial alpha(k) (molar ratio of Na2O and Al2O3 in aluminate solution) could lead to the increase of average crystal size while the increase of agitation speed had an adverse effect. The growth rate, the nucleation rate and the aggregation kernel were determined using a volume-independent growth aggregation model. The calculation of aggregation kernel was divided into two parts in terms of crystal size: smaller than 10 mu m and larger than 10 mu m. Results implied that small crystals below 10 mu m aggregated more significantly than large crystals. The aggregation dominated the enlargement of small crystals, but the enlargement of large crystals mainly stemmed from the growth rather than the aggregation.