The invention discloses a high-sintering active indium tin oxide mixed powder preparation method. The method particularly comprises the steps that high-activity nano SnO2 powder is prepared, wherein a compound dispersing agent is dissolved into water, an appropriate amount of SnCl4 is added, stirring is conducted till the mixture is completely transparent, and clarification is conducted; stirring is kept, an appropriate amount of ammonium hydroxide is added, a tin-containing precursor is obtained, after the precursor is placed in a high pressure reaction kettle to be subjected to hydrothermal treatment, sediment is taken out to be washed repeatedly, dried and subjected to low temperature thermal treatment, and nano SnO2 powder is obtained; metal indium is dissolved into hydrochloric acid, a InCl3 aqueous solution is generated, and a method similar to the method for synthesizing SnO2 powder is used for preparing nano In2O3 powder; the prepared InCl3 is mixed with SnO2 in proportion, PVA is added, by means of a spray drying technology, mixed indium tin oxide granulation powder which is less in aggregation, good in liquidity and prone to pressure molding is obtained, and the preparation method can be suitable for preparing high-end ITO target materials.