Abstract: A new technology of preparing light magnesium carbonate and by-producing ammonium sulfate,with magnesium sulfate heptahydrate as raw material and with ammonium bicarbonate as precipitator,was put forward.Effects of process conditions,such as mass fraction of magnesium sulfate solution,reaction temperature,and pyrolysis temperature etc.on the quality of light magnesium carbonate,were investigated.Results of orthogonal experiment showed that pyrolysis temperature is the most significant factor on purity of product.And the product can meet the quality requirement of high-class product stipulated by HG/T 2959—2000 when mass fraction of magnesium sulfate solution is 40%,reaction temperature is 35 ℃ and pyrolysis temperature is 90 ℃.