The invention discloses a preparation method of an ultrathin B phase 
titanium dioxide nano sheet, and relates to the field of 
titanium dioxide. The preparation method comprises the following steps: (1) adding a 
titanium precursor into glycol, and stirring to obtain a glycol-titanium solution; (2) adding water into the glycol-titanium solution obtained in the step (1), stirring, carrying out reactions at a temperature of 150 to 180 DEG C, and subjecting the obtained turbid liquid to 
centrifugation so as to obtain white precipitate; (3) washing the white precipitate obtained in the step (2), and 
drying white precipitate in the air to obtain the ultrathin B phase 
titanium dioxide nano sheet. The preparation method has the advantages that the raw materials are cheap, little 
sulfuric acid is used, the output of waste byproducts is little; the 
reaction temperature is mild and is far lower than the 
boiling point of glycol; the reaction pressure is not high and thus is benefit for amplification operation; the thickness of the prepared ultrathin 
titanium dioxide nano sheet is less than 2 nm, the nano sheet appears typical characteristics of a two-dimensional material; the 
operability is strong, the reaction apparatus is simple, the synthesis and 
post treatment conditions are mild, the conditions during the preparation process are mild, the reaction process is clean and 
pollution-free, and the reaction efficiency is high.