Abstract: Nesquehonite was synthesized by using brine as the source, and the influence of additives on crystal phase regulation, self-assembly and the pyrolysis process of the product were researched. The results showed that the adding of seed crystal with 1% (w) could shorten the induction period of product, and increase the aspect ratio; products uniform in length and high in the aspect ratio could be obtained by adding ethanol; sheaf structured products could be obtained with glycerol; the adding of sodium dodecyl sulfate could make the aspect ratio increase from 29.6 to 35. Nesquehonite was an ideal precursor to prepare other departments of magnesium products due to its low pyrolysis temperature and high purity.