The invention relates to a preparing process for a calcined kaolin for a butyl rubber plug, which is characterized in that the process comprises the following procedures: washing the crude kaolin minerals, conveying them to a jaw crusher to coarsely crush into pieces below 10 mm; then pulverizing fine by a machine, meanwhile adding some pulverizing assistant 760 accounting for 0.5-1% by mass of crude kaolin minerals through a vibration feeder, scattering and grading, so as to get graded powder; sending the graded powder into an intercalating kiln to mix and intercalate with urea, the additionamount of which is 3-5% of the graded powder; scattering the intercalated powder by clone, then sending the powder into a vertical calcining kiln under 900-950 DEG C, scattering and grading again, soas to get calcined kaolin for a butyl rubber plug with particle size of 2 micro meter accounting for more than 80%, and whiteness more than 80. The product from the invention is of low content of foreign matters, fine particle size and high whiteness.