Large size of YCa<sub>4</sub>O(BO<sub>3</sub>)<sub>3</sub>(YCOB) crystals were grown both by Czochralski and Bridgman methods. Large size elements as large as 60 mm clear aperture were cut and polished with surface flatness of 1/5 wavelength. Optical
homogeneity of YCOB crystal was found in the order of 10<sup>-6</sup>. Laser damage thresholds of several YCOB crystal
elements were tested using different laser facilities with different pulse widths or wavelengths, with thresholds varied
from 0.8 GW/cm<sup>2</sup> to more than 1 TW/cm<sup>2</sup>. One SHG and two optical parametric chirped-pulse amplification (OPCPA)
experiments were executed to characterize the nonlinear optical properties of YCOB crystals and the quality of the
crystals. The results shown that YCOB had good performance in OPCPA application, especially with low content of
parameter florescence. Combined with good NLO performance and possibility to grow large size crystals, YCOB crystal
was a good choice for high power OPCPA applications.