Cement mortar for small size float collars and small size float shoes, and preparation method thereof

The present invention provides a cement mortar for small size float collars and small size float shoes, wherein the cement mortar comprises 15-30 wt% of cement, 50-60 wt% of fine aggregate, 2-5 wt% of silica fume, 3-5 wt% of fly ash, 0.2-1 wt% of an early strength agent, 3-5 wt% of an expander, 0.2-0.8 wt% of a water reducing agent, and 5-15 wt% of water. With the cement mortar of the present invention, the disadvantage that the cement mortar in the prior art can not be used for filling the gap of the small size float collars and small size float shoes can be overcome, and the correspondingly-required compressive strength and the correspondingly-required impermeability can be met.