Single crystal of LiNbO3has been successfully grown by the Czochralski method in an air atmosphere with a r.f heating crystal growth system namely Automatic Diameter Control Crystal Growth System (ADC-CGS). This paper reports on the effect of new thermal insulation on the growth process of LiNbO3single crystal. The effect of hot zone thermal insulation design was investigated. The conditions required to grow high quality LiNbO3single crystals are described. A set of crystal growth processes were conducted with the rotation rate of the seed at 15 rpm and the pulling rate at 2.0 mm/hr kept constant. All of the runs were grown along <104> orientation. To control the diameter of the crystal, we have to alter the thermal environment inside the hot zone. In other words, during the crystal growth we have to increase the control power to get smaller diameter and decrease the control power to get larger diameter.