The invention discloses a solvent-thermal method for preparing single-phase bismuth titanate Bi2Ti2O7. Bismuth nitrate and butyl titanate are taken as raw materials, and the method is characterized by comprising the following steps of: dissolving the bismuth nitrate in alcohol serving as a solvent, and adding the butyl titanate and ether, wherein the using amount of the bismuth nitrate is lower than the stoichiometric ratio; uniformly mixing, and reacting at the temperature of between 110 and 230DEG C in an enclosed reaction kettle; and cooling, filtering and drying a solid, and calcining at the temperature of between 450 and 550DEG C to obtain the single-phase Bi2Ti2O7. The prepared bismuth titanate compound has a single-phase structure, is spherical nanoparticles, and has excellent solar photo-catalytic activity. The method has the advantages of low synthesis temperature, high powder purity and the like, the preparation process is simple, the raw materials are readily available, thecost is low, and the equipment is simple, and easy to operate.