The invention discloses a method for preparing calcium titanate nanoparticles. The method comprises the following steps of: adding a mineralizing agent, namely potassium hydroxide, with proper concentration, into hydrothermal reaction materials, namely titanium hydroxide coprecipitate and deionized water solution of calcium nitrate; introducing solution obtained by hydrothermally decomposing glucose into a hydrothermal system to influence nucleation and control the particle size of products; and synthesizing the calcium titanate nanoparticles of which the diameter is 30 to 60nm by hydrothermal reaction. The process is simple and is easy to control; the method is environment-friendly and low in cost; and the products are easy to produce.