Nd xGd 1-xCa 4O(BO 3) 3 (NdGdCOB) i s a new self-frequency-doubling (SFD) solid-solution crystal. The second-harmonic generation (SHG) phase-matching (PM) curves were calculated by using refractive indices. The d eff of NdGdCOB crystal along different PM directions were calculated according to the sellmeier equation and d ijk data in which the (θ=66.8°, φ=132.6°) PM direction has the highest d eff. SFD experiments were carried out with Ti∶sapphire CW laser and pulsed dye-laser. A green laser output power up to 225 mW at 530 nm was achieved from a 7×3×3 mm-3 crystal sample pumped by 1560 mW CW Ti∶sapphire laser. The lasing threshold of SFD was lower than 1.8 mW along the PM direction (66.8°,132.6°). The optical-optical conversion efficiency was 14.4%. The conversion efficiency was 7.7% when 10×3×3 mm-3 sample was side-pumped by the pulsed dye-laser tuned to 595.4 nm with 17.5 mJ energy and the lasing threshold is 1.2 mJ. Nd xGd 1-xCa 4O (BO 3) 3 (NdGdCOB) isa new self-frequency-doubling (SFD) solid-solution crystal. The second- . The d eff of NdGdCOB crystal along different PM directions were calculated according to the sell equation and d ijk data in which the (θ = 66.8 °, φ = 132.6 °) PM direction has the highest d eff. A laser output power up to 225 mW at 530 nm was achieved from a 7 × 3 × 3 mm-3 crystal sample pumped by 1560 mW CW Ti: sputtering laser. The lasing threshold of SFD was lower than 1.8 mW along the PM direction (66.8 °, 132.6 °). The optical-optical conversion efficiency was 14.4%. The conversion efficiency was 7.7% when 10 × 3 × 3 mm-3 sample was side-pumped by the pulsed dye-laser tuned to 595.4 nm with 17.5 mJ energy and the lasing threshold is 1.2 mJ.