A process for co-production of aluminum titanate powder and an acid is provided. The process includes mixing and grinding phosphogypsum, fly ash, an additive and a modifier to obtain a raw material, and roasting the raw material in a kiln to obtain a clinker; subjecting the clinker to dissolution, and performing solid-liquid separation; preparing alumina from the separated liquid; fully mixing theobtained alumina with titanium dioxide, magnesium oxide, cerium oxide, ferric oxide, silicon oxide, zirconium oxide and cobaltous oxide; adding deionized water into the mixture, and mixing, grindingand drying the mixture to obtain a mixed material; sintering the mixed material; cooling and then crushing the mixed material; adding deionized water into the mixed material; grinding the mixture, andperforming spray-drying to obtain the aluminum titanate powder; subjecting residual dregs obtained by separation to floating to obtain sulfides; and processing the sulfides to prepare sulfuric acid.The process has advantages of low costs for preparing the aluminum titanate powder and the acid and a high residue utilization rate, and the prepared aluminum titanate powder has high quality and a simple process.