Low-true-density kaolin rubber reinforcing filler and preparation method thereof

The invention discloses a low-true-density kaolin rubber reinforcing filler and a preparation method thereof, and the preparation method comprises the following steps: taking kaolin as a raw material, carrying out dry crushing on the kaolin to obtain a coarse material, adding water and an alkali metal compound auxiliary agent into the coarse material, carrying out wet ultrafine grinding, then carrying out centrifugal classification to obtain ultrafine slurry, and carrying out vacuum drying on the ultrafine slurry to obtain the low-true-density kaolin rubber reinforcing filler. The proportion of kaolin smaller than or equal to 2 microns in the superfine slurry reaches 95% or above; carrying out spray drying and depolymerization on the superfine slurry to obtain fine material particles; mixing the fine material particles with air to obtain suspended solids, spraying the suspended solids into a calcining kiln in a jet manner for flash calcining, and cooling to obtain the low-true-density kaolin rubber reinforcin