This paper presents a new control technique for handling the tube wall temperature and mass production rate of Vinyl Chloride Monomer (VCM) in a cracking furnace by taking advantage of finite element method and Input–Output (I/O) linearization. I/O linearization technique is extended to apply to a coupled PDE–ODE system. A finite element based, open-loop state observer is used to estimate the information of the process states and state derivatives. The feedback I/O linearizing controller is designed to force the tube wall temperature to follow a desired trajectory. To handle the mass production rate of VCM, an EDC feed velocity controller with a proportional-integral structure is formulated. The control performances of the developed control method are demonstrated through servo and regulatory tests.