A highly stable, reproducible and water-based bismuth titanate (BTO) sol system has been synthesized by an aqueous sol-gel method. First bismuth nitrate was dissolved in acetic acid, and then it was mixed with a solution of lactic acid dissolved tetra-n-butyl titanate, subsequently, water was added to adjust sol concentration. As-obtained sols or gels were characterized by Ultraviolet-Visible Spectrophotometer, derivative differential thermal analysis-differential thermal analysis-thermal gravimetry, in situ Raman, and high-temperature X-ray diffraction. Results show that the BTO sol can remain stable for more than 1 year and BTO can start to crystallize at about 450 degrees C.