The crystalline phase formed during aluminum titanate at 750–1300 ℃ as well as the relationship between its content change and decomposition dynamics was mainly discussed in this paper. Dynamical equation was established for calculating the reaction activation energy. It aimed at providing dynamics basic data for taking up necessary measures to inhibit the decomposition of aluminum titanate. Experimental results showed that aluminum titanate would decompose into TiO₂ and corundum at 750–1300 ℃. Content of aluminum titanate would reduce with the increase of decomposition time, and the order of decomposition rates at different temperature was 1100 > 1200 > 1000 > 900 ℃. The decomposition was a chemical reaction with control steps, and could meet the first order reaction dynamic equation- F(G) = [(1 – G)^-2/3 – 1] = Kt. According to the calculation, rate constants of different decomposition reaction dynamic equations were K₉₀₀ = 2.2×10^-3, K₁₀₀₀ = 1.2×10^-2, K₁₁₀₀ = 4×10^-1 and K₁₂₀₀ = 1.5×10^-1, and the reaction activation energy ΔGave = 203.21 KJ/mol.