In this article, a mesoporous commercial alumina was calcined in the temperature range of 600 degrees C-1200 degrees C. The effect of several parameters such as calcination temperature, calcination time, heating rate, and calcination steps on phase transformation and crystal size was experimentally investigated. The characterization of the commercial mesoporous alumina and samples calcined at 1000 degrees C, 1040 degrees C, 1070 degrees C, 1100 degrees C, and 1200 degrees C by single-step and multi-step calcination was performed using XRD and N-2 adsorption/desorption techniques. For the commercial mesoporous alumina, TG/DTA analysis was also performed. Experimental results showed that mostly pure alpha-Al2O3 was obtained at 1100 degrees C.