The invention relates to a nanotin dioxide piezoresistor composite powder material. The material is prepared from tin dioxide, bismuth trioxide, antimony trioxide and yttrium trioxide. The preparation method is characterized by preparing the high-performance nanotin dioxide composite powder by adopting a forced micromixing method and a colloid mill as a reaction container through a nucleating/growth isolation method. The preparation of the nanotin dioxide piezoresistor composite powder with excellent performance is a crucial to obtaining of a high-performance piezoresistor. The forced micromixing technology is adopted during nucleating/growth isolation preparation, a salt solution and an alkaline solution are fast and fully mixed at a gap between a rotor and a stator of the reactor, so that the material has the characteristics of being small in particle size and uniform in distribution; zinc element and other modification elements can be coprecipitated during the growth of crystal grains, so that the microscopic uniformity of the composite powder can be improved. Therefore, the nanotin dioxide piezoresistor composite powder which is small in grain size, uniform in the distribution of modification oxides, and narrow in the distribution of grain sizes can be obtained.