Semi-batch and batch-wise reactive crystallization of Li2CO3 was carried out in the presence of magnesium chloride. Magnesium impurity restrained crystal growth, and modified the crystal shape as well as crystal size distribution. However, the added magnesium impurity was usually contained in the product crystals. There was an optimal range for the amount of magnesium impurity. In this study, the influence of temperature was also investigated. In general, the solubility of lithium carbonate decreases with temperature, and it is higher than other sparingly soluble compounds such as CaCO3 and BaSO4. In this study, higher temperatures (70 degrees C and above) were better for obtaining homogeneous crystals because higher supersaturation was possible.