The invention discloses an anti-freezing cement asphalt mortar and a preparation method thereof. The cement asphalt mortar comprises emulsified asphalt, cement, fine sand, an expansive agent, an aluminite powder and water. A formula of the emulsified asphalt comprises asphalt, an anionic emulsifier, a cationic emulsifier, a thickener, a stabilizer, a water reducing agent, a defoaming agent, alcohol and water. The cement asphalt mortar provided by the invention employs special emulsified asphalt; and when the cement asphalt mortar is mixed with dry material such as cement and sand, the water reducing agent and the defoaming agent are easily dispersed to fully contact with the dry material, thus realizing obvious water reducing effect, effectively avoiding bleeding phenomenon after pouring of CA mortar, and improving workability of the emulsified asphalt with cement and fine sand; and synergistic effect of alcohol improves anti-freezing performance of the CA mortar, effectively eliminates large bubbles, and realizes dense and uniform texture after forming of the CA mortar. The cement asphalt mortar provided by the invention is particularly suitable for perfusion under track plate as a buffer layer in construction of high-speed railway.