The invention relates to an improvement on structure of crystal growing furnace for pulling alumina single crystal and method for growing alumina single crystal, and the structure improvement is that a cylinder cavity body is in a thermal insulator, the cylinder type cavity is placed with a crucible, and the external part of the thermal insulator is provided with a heating wire. The structure improvement is characterized in that the upper side part of the thermal insulator has at least one opening, and the middle part of the upper part of the thermal insulator is provided with an opening, and oxygen and inactive gas flow into the cavity from the opening, and the gas flows out from the opening, and the opening is the port for the seed crystal to arrive at the solution. The mixing gas composed of oxygen and inactive gas is used in the growing process, and the concentrations of oxygen in the mixing gas at different steps are different; and a purifying process is added. The invention can effectively inhibit bubble generation in the crystal, and service life of the crucible is long without vacuum-pumping, and not only c-plane alumina single crystal, but also r-plane, m-plane or n-plane white alumina single crystal can be pulled.