The bonding structure of laser-prepared nanometer a-SixNy:H powder and the bulk body prepared by pressing of powder are studied by IR and Raman spectroscopy. It is found that there are Si-N Si-Si, Si-H, N-H, Si-O-Si bonds and OH group in a-SixNy:H. The distortion of the spectra and the change of bonding structure of the bulk body before and after annealing are discussed.