The invention relates to cement slurry with a controllable rheological property and a preparation method thereof. The cement slurry has the technical scheme that the cement slurry with the controllable rheological property is prepared by the following steps: by using 30 to 50 weight percent of calcium aluminate cement and 50 to 70 weight percent of alpha-aluminum oxide micro powder as raw materials, uniformly mixing the raw materials; then, adding silica sol accounting for 1 to 50 weight percent of the raw materials and water accounting for 35 to 40 weight percent of the raw materials; performing stirring for 3 to 8 minutes to obtain the cement slurry with the controllable rheological property. The Al2O3 content of the aluminate cement is higher than 53 weight percent, and the CaO content of the aluminate cement is higher than 21 weight percent; the silica sol concentration is 1 to 50 weight percent, and the particle diameter is 5 to 100nm. By using raw materials and methods easily realized in the engineering, the characteristics that the process is simple and the engineering application applicability is realized are achieved. Compared with cement slurry prepared in the prior art, the prepared cement slurry with the controllable rheological property has the advantages that the rheological property is controllable; the initial setting-final setting time interval is short.