The invention relates to mortar composition and a preparation method thereof. The mortar composition is prepared from a gel material, a sandy material, a thickener, a water reducer, a water retention defoaming agent and an early strength agent. The composition has high cement property, high strength, high crack resistance and good pumping performance. What needs to be pointed out is that the sandy material with different particle sizes is formed in a certain ratio in the composition, the mechanical properties, such as compressive strength and breaking strength, of the composition after coagulation are improved.