The Nb:KTP crystal was grown from the raw material containing different concentrations Nbjj06 by top-seed flux method in improved Ke melt The largest one weight 60 grams and the transparent area is 15 mm×l7 mm×14 mm dimension. Their transmission are more than 85% at the applied wave range. The cut-off wavelength has blue-shifted to 937 nm.The 468.5 nm and 473 nm as well as 480 nm blue lasers were obtained by different Nb doped KTP crystals. The principle refractive indices of 7.5 mol.-% Nb:KTP were measured The angle, temperature and spectral acceptance bandwidth were calculated for the crystal and then compared those with KTP and KNbO3. The results show that they are 2.6, 24 and 3.4 times those of KNbO3 crystal. Therefore, the applied condition will be relaxed and the frequency doubled performance will be improved.