The invention relates to a rosuvastatin calcium preparation intermediate, and a method for preparing rosuvastatin calcium from the intermediate. The intermediate compound 1-a being able to realize easy control of the purity of optical isomers in the rosuvastatin calcium preparation process undergoes cyclic carbonate protection group removal under an alkaline condition to prepare the rosuvastatin calcium, the purity is 99.5% or above, and almost no optical isomer are generated, so the impurity control difficulty is greatly reduced, and the high quality level of the product rosuvastatin calcium is guaranteed. The method selecting a short route and mild reaction conditions to prepare rosuvastatin calcium reduces the difficulty of a technologic device and operation, so industrialization is easy to realize.