A new precipitation route to ammonium aluminum carbonate hydroxide (AACH) was presented. There was an incubation period before AACH precipitated. Effects of synthesis parameters such as pH of ammonium hydrogen carbonate solution, precipitation temperature, concentration of aluminum citrate and type of anions on the precipitation of ammonium aluminum carbonate hydroxide were discussed. It was found that the incubation period decreased with the increasing pH of AHC solution, concentration of aluminum citrate and the decreasing reaction temperature. Compared to NO3 -, SO4 2- delayed the formation of AACH and enlarged the particle size of AACH.