A system based on the infrared image and the heat transfer mechanism of radiation and convection is developed to measure the heat loss of rotary kiln through the kiln shell, with which the models of the total heat loss is derived for heat loss calculation. By using LabVIEW programming language, a software is then developed to measure the heat loss. The effectiveness of the proposed method is tested by using a cement rotary kiln as example. It is shown that, the system is able to capture the axial temperature of the kiln shell of interest and calculates the corresponding heat loss correctly. It is also found that the heat loss through radiation has similar magnitude to the heat loss through convection, and the heat loss in the burning zone is about 4% of the total input thermal energy into the kiln. The result of the present work has potential usage in the energysaving production and optimization of process parameters.