Novel magneto-optical crystals are highly demanded to meet the rapid development of high-power laser machinery. The Tb3Al5O12 crystal has been demonstrated to be an excellent magneto-optical crystal, however, only small-sized single crystals can be produced so far due to its incongruent melting behavior. Herein, a Tb3Al4GaO12 crystal with Ga3+ substitution through the TGG structural modulation was designed to improve the bulk single crystal growth. It has been successfully grown by the Czochralski method for the first time. The crystal exhibits superior transmittance of over 80 % and enhanced Verdet constant (∼1.2–1.3 times that of TGG crystal), suggesting a promising application for high-power lasers.