Research conclusions: Based on the construction practice of cement emulsified asphalt mortar cushion for a CRTSII slab ballastess track of one high － speed railway， the analysis is made for the causes for the common problems after pouring in the course of construction of，namely，the micro cracks happen in the joint area between the slab and the mortar or the mortar is not full and slices in some areas，and a large number of the tiny bubbles，the larger bubbles，the bubbles of connecting each other from top to down happen and the asphalt bead separate out． The relative measures are presented from the fields of the edge banding technique for the track slab，the pouring technique，the mixing technique and thecontrol of raw materials to improve the construction quality and it can be as the reference to the similar works．