A high-power diode-side-pumped 1 110 nm Nd：GGG laser and a laser at 555 nm based on intracavity frequency doubling of 1 110 nm laser were demonstrated for the first time. A simple straight cavity scheme was employed to achieve a compact configuration and all the coatings were designed specially. A 25.5 W 1 110 nm laser continuous wave output was achieved under the incident pump power of 168 W. A LiB3O5(LBO)crystal was used for second harmonic generation of the laser. As a result, at the pump power of 168 W, the maximum power of the frequency-doubled output at 555 nm was found to be 3.1 W with a pulse repetition rate of 10 kHz, corresponding to an optical-to-optical conversion efficiency of about 1.8%. And the pulse width of 555 nm wave was 176 ns. The M2 factors are measured to be 19.6 and 21.3 in the horizontal and vertical directions, respectively.