Premixed combustion is widely used for reducing pollutant emission from combustion chambers. However, these systems may be sensitive to complex phenomena such as flashback. In the present study flame, flashback and structure of premixed laminar flames are investigated theoretically. The mathematical model includes the axi-symmetric continuity, Navier Stocks, energy, and species equations. Combustion is modeled as one-step overall reaction using experimental relation with Arrhenius finite rate model. Flashback is examined as a function of wall velocity gradient, tube radius, and fuel concentration in mixture. The analysis is done in two stages. In the first stage, analysis is done traditionally where the value of flashback criteria is calculated and the unstable region of combustion is obtained. In the second stage, flame is kept to propagate into the region of investigation to study the flame structure. Because of complexity of flame flashback, difficulties of performing the experiments confronting flashback phenomena, and fire hazard, the numerical simulation of this phenomenon is strongly recommended.