A film of nanocrystalline silicon embedded in SiNx (nc-Si/SiNx)was prepared by radio-frequency magnetron sputtering technique and thermal annealing. By using the film as a saturate absorber, a 946 nm laser with passive Q-switching was achieved in a laser diode (LD) continual end-pumped Nd:YAG laser and a 473 nm blue laser pulse was generated with intra-cavity frequency doubling of LiB3O5(LBO) crystal. At the pump power of 8.5 W, the Q-switched blue laser pulses with average power of 120 mW, pulse duration of 45 ns, repetition rate of 23.8 kHz and peak power of 112 W were obtained. The conversion efficiency from pump lasers to 473 nm blue laser pulses was 1.41%. The changes of average powers, pulse repetition rates and pulse duration of the blue laser pulses with pump powers were experimentally studied. Theoretical analysis showed that the two-photon saturate absorption at 946 nm laser pulse in nanocrystalline silicon embedded in SiNx films caused the passive Q-switching of Nd:YAG 946 nm lasers.