Abstract: In actual production，people often pay attention to raw material decomposition rate in the kiln，but few of them consider characteristics of decomposition product of raw material.Influences of different temperatures on the reaction of CaCO3 and on product activity under suspended state were investigated with a high temperature one-dimensional furnace.The results showed that under the same resident time，decomposition rate of CaCO3 at 900 ℃ was 26.0%，and 67.1% at 1150 ℃. Because the decomposition product under 1 150 ℃ had finer grains，higher porosity，and greater specific surface area，cumulative hydration heat of decomposition product CaO under 1 150 ℃ was higher near 4 times than that of 900 ℃，and hydration activity was greatly enhanced.Then clinker burning process may be speeded up by using this characteristics.

Key words: suspended state, calcium carbonate, temperature, decomposition