A various study on premixed combustion is under way to make effectively a designing and operation on combustion machinery. This paper includes contents of numerical analytic study on various flame structure occurring in premixed combustion on closed tube. A numerical method for the analysis of CH4-Air premixed flame is presented with the scrutiny into the flame structure and propagation behavior. The continuity, momentum, energy and mass fraction equation with standard k- turbulence model were solved utilizing ANSYS-Fluent solver. And also G-equation model is employed for analysing properties in premixed combustion. This model was chosen because it is famous for premixed flame-front tracking model and having high accuracy about that. To verify the validity of numerical simulation method on premixed combustion applied on this paper, numerical results were compared with experimental data. As a numerical results, it is confirmed that flame structure changes in the order of hemispherical flame, flat flame, and tulip flame. In addition, the detailed analysis on each flame structure is conducted using vectors and contours. And also, it is confirmed that the velocity of flame propagation is changed depending on the flame structure. Just after ignition, the flame velocity increases dramatically. During hemispherical flame, it shows the uniform speed. But in the transient zone which is flame structure changes from hemispherical flame to tulip flame, the flame propagation speed decreases rapidly. After forming a tulip flame perfectly, the flame velocity maintain a uniform speed generally. It is considered that these phenomenon shows up because various affects such as reverse flow, vortex, and turbulence flow and so on. And also, the detailed investigation about flame thickness on each flame structure is conducted too.