Combustion using combustion air with the condition of 1010°C and 3.0% oxygen content diluted air, has shown unique characteristics. A high flame stability, flame volume enlargement, greenich flame color and low NO_x emissions were the characteristics of the combustion named here as high temperature air combustion. Flame with an enlarged volume having low flame luminosity was one of the important findings which implies a heat release rate in unit space of the flame decreased. The flame temperature profile thus became more homogeneous than ordinary flames. This potential that the high temperature air conbustion may improve thermal field uniformity can cause a revolution of combustion technology on the high performance industrial furnace design.