Ethylene and propylene are among the light olefins which are the main building blocks in the petrochemical and chemical industry. They are produced from thermal/catalytic cracking of gaseous and liquid hydrocarbons and recently from methanol. This paper continues the two review articles published before entitled thermal and catalytic cracking of hydrocarbons for the production of light olefins. In the last two review articles, the processes and the kinetics of thermal and catalytic cracking have been discussed in details. This paper reviews the mathematical modeling and simulation of the olefin plants including mechanisms and kinetic models, CFD simulations, rigorous models, and abstract models.