Cement-asphalt mortar is the key engineering material in the slab track system of high-speed railways. This material commonly used as a cushion layer for this structure which is injected in between the track slab and concrete roadbed and its mechanical properties play an important role for a smooth and safe ride. Cement-asphalt mortar mainly consists of cement, asphalt emulsion, fine aggregate and several chemical admixtures. This material is commonly used in prefabricated slabs, including Shinkansen and Bogl lines, with the aim of adjusting line geometry during construction.‏ as respects these two types of railway tracks are the largest share of slab track made around the world, it is essential to examine different parts of it. In this paper, firstly, the cement-asphalt mortar has been introduced. In the following, the requirements of this type of mortar have been investigated in different parts, including primary materials and construction.