Moderate and intensive low-oxygen dilution (MILD) combustion is a new combustion technology. It features as combustion under a hot and diluted oxidation condition. The objective of this article is to optimize global mechanisms for predicting the major species concentration of CH4 combustion under MILD condition. For this purpose, six different global combustion mechanisms, including the four-step mechanism of Jones and Lindstedt (1988), the two-step mechanism of Westbrook and Dryer (1981), and several modified versions of them, were investigated. Reference calculations were also conducted with detailed chemical kinetic mechanism GRI-Mech 3.0. The interaction between turbulence and chemistry was modeled by eddy dissipation concept (EDC). All of these global mechanisms are validated first by a fictitious plug flow reactor and then by a non-premixed turbulent jet flame of a H-2/CH4 fuel mixture (Dally et al., 2002). The results show that modified the Westbrook and Dryer mechanism (WD4), which includes both CO oxidation rate and H-2 oxidation rate modification, shows the best agreement with experiment.