According to the analysis of chemical and mineral components of building mortars from the Ming Dynasty to the Republic of China, some masonry and plastering mortar is dolomitic lime or magnesium lime, and the content of MgO ranges from 5% to 26%. In particular, all mortar samples from the Great Wall belong to dolomitic lime. Compared with calcium lime, dolomitic lime boasts higher strength, lower water absorption, lower shrinkage and better workability; therefore it is more frost-resistant than calcium lime. In addition, the temperature and energy required for calcining dolomitic lime is lower than that required for high-calcium lime. It is recommended that further research on dolomitic lime be carried out systematically in China, and that it includes the type and distribution of raw material, calcination temperature, slaking, optimal formulation and technologies for restoration, etc. At the same time, it is suggested that further research also be carried out on the durability of dolomitic lime under atmospheric industrial pollution, as well as the conservation and restoration technologies for dolomitic lime-related architectural heritages.