Hydraulic mortars are traditional construction materials with good properties. Compared with air-hardening mortars, hydraulic mortars possess better waterproofness, permeability, freezing resistance, salt crystallization resistance and mechanical strength, and are potentially ideal restoration materials for historical architecture. The present research reviews factors influencing the properties of traditional hydraulic mortars, including inorganic components (binder, aggregate and water), natural organic additives (polysaccharides, proteins, oils and fats), and curing conditions. For inorganic components, their influences on hydraulic mortars depend on both the properties of the binder and the proportions of the different inorganic components. For natural organic additives, addition of polysaccharides into mortars can improve their mechanical strengths, addition of proteins can increase their water resistance and porosity, and addition of oils and fats can greatly improve their water resistance and durability. As for curing conditions, hydraulic mortars cured under higher relative humidity can have better mechanical strengths, while those cured under low relative humidity are more durable. The present research intends to contribute to understanding the scientific values of traditional hydraulic mortars, and to developing new restoration materials for historical architecture as well.