The invention discloses a method for synthesizing a spherical lithium tantalate doped polycrystal raw material with even compositions. The method comprises the following steps that: tantalum source raw material is evenly mixed in an organic solvent containing a carboxylic group to form a coordination compound containing tantalum , the accurate content of the tantalum is calculated by a thermogravimetric analysis method, Li<+>, MgO or ZnO is added, the even mixing of the doped elements and the substrate material in the atom grade is realized by the magnetic stirring, the sprayer drying granulation technique is adopted to realize the control of the grain diameter of the polycrystal material, and the material is synthesized by the sintering process at a temperature lower than the solid phase reaction temperature. The polycrystal material synthesized by the method has the primary particle size in the nano scale, and the melting point which is evidently lower than the solid phase reactionpolycrystal material, thereby not only saving energy, but also realizing the automation of the lithium tantalate crystal growth by dopting the stoichiometry ratio as for the continuous feeding growthtechnology.