Abstract: As the key material used in high-speed railway to reduce vibration in the slab track, CA mortar mainly includes cement、asphalt emulsion and multiple additives.Among all additives, water reducer is the important component.In order to study the influences of water reducer of different types and additions on the strength and micro-structure of CA mortar, three kinds of water reducers of polycarboxylate, naphthalene sulfonate and wood series, were used with different additions to investigate their influences on the strength of CA mortar, meanwhile, the micro-structure were observed by SEM method.The results show that, the polycarboxylate water reducer has the lowest effect to decrease the CA mortar strength.When the types of water reducer are the same, the more the water reducer are, the more the strength decrease.By the SEM observation, the reasons of strength changing of different CA mortars can attributed to the differences of the pore volume, pore size and pore connectivity.