The improved process is achieved by introducing depuration of green liquor and lime before causticization and two special causticization steps in causticization procedure of conventional chemical recovery processes. It not only avoids the generation of waste residue (lime mud) from the beginning and saves the re-burning and filling land of lime mud, but also can directly produce a series of precipitated calcium carbonate products with various particle sizes by regulating process conditions while alkali is recovered. The CaCO.sub.3 products include CaCO.sub.3 wherein .gtoreq.50% of CaCO.sub.3 has a particle size below 2 .mu.m, CaCO.sub.3 wherein .gtoreq.90% of CaCO.sub.3 have a particle size below 2 .mu.m, and a superfine CaCO.sub.3 having an average particle size <1 .mu.m. The CaCO.sub.3 obtained by this process can be directly used for papermaking and other industrial applications.