The invention relates to an impregnation drying process of a chromium series microspheric fluid bed isobutane dehydrogenation catalyst. The process is innovative by comprising the steps of: S1, a preparation process: first, adding a microspheric alumina carrier to a rotary vacuum impregnation dryer; S2, preheating: heating the alumina carrier to 30 DEG C-50 DEG C, and stopping heating; preparing an immersion liquid containing the chromium component, and heating the impregnation liquid to 50-55 DEG C outside the rotary vacuum dryer; S3 prepreg: starting a vacuum rotary impregnation machine, stirring, and spraying the impregnation liquid onto the alumina support; and S4, dipping drying process: conducting vacuum drying. The present invention has the advantages that: the catalyst carrier has good impregnation effect, no requirement of multiple impregnations and high efficiency; the catalyst prepared by the post-process has uniform distribution of the catalytic active components; and the process is especially applicable to chromium series microspheric fluid bed isobutane dehydrogenation catalyst dried by a fluid bed in the late stage.