The effect of blowing or suction on free convection heat transfer about a vertical flat plate is analyzed by an approximate method by using the integral formulas for momentum and energy equations. There are similar solutions, if the surface temperature distribution is expressed by the equation T_w=T_∞+Axⁿ (x : distance from leading edge, A and n : constants, T_∞ : temperature in quiescent ambient fluid) and the blowing or suction rate distribution is proportional to x^(n-1)/4. Approximate similar solutions found under these conditions may be applied for any exponent n (0⪈n⪈1) in a power law surface temperature distribution and the gases for any Prandtl number, if the blowing or suction Reynolds number is restricted within the following ranges. At n=0 [numerical formula] At n=1 [numerical formula] where ν is the kinematic viscosity of fluid and G_rx denotes the local Grashof number at the position x.