Cooler is the key device of rotary calcining kiln to produced limestone. Through design processes, better heat exchange can be obtained. According to the structural features and working principles of rotary calcining kiln, the finite element model of cooler is built. Then the convection heat transfer coefficient is calculated on the theory of heat transfer. On the simulation analysis of the heat transfer of the cooler based on the Flotran of ANSYS, the distribution of temperature in cooler is given. The results show that the surface temperature drops to 450 O C, after which it gradually rise until maturity. In additional, the convection heat transfer coefficients increase with the velocity of gas at the entrance of cooler. So the low-temperature region increases and more limestone down to a lower surface temperature.