Abstract: In this paper, two examples in chemical processes (styrene suspension batch polymerization and ethylhenzene dehydrogenation) are given to indicate the extended application of the model-based measuring technique using state estimation to practical industrial objects. It can provide for operation supervision, monitoring and optimal control the information about a process which is usually immeasurable but necessary to process operation. Such information is directly related to product quality, e. g., chain length distribution of polymer, catalyst activity, inversion rate of reaction process, selectivity, etc. In this paper the modelling, control design and implementation for the two reaction processes are also introduced. Some experience for the application in industrial processes has been accumulated.