The properties of Si-H bonds and H-induced defects in single crystal silicon were investigated by means of photoluminescence, nuclear magnetic resonance and electron spin resonance. The results of photoluminescence indicate that the Si-H bonds induced a lot of non-radiative centers. The relation of average thickness of samples to electron spin resonance measurement was observed and discussed.Our work overcomes the difficulties in association with diffusion of H through the surface during annealing in vacuum and with ESR measurement when the thickness of the samples was over 1.00 mm or less than 0.85 mm. in comparing the ESR results for single crystal silicon grown in hydrogen and that in argon atmosphere, we got the amount of hydrogen to be 4×l016cm-3 and the activation energy to be about 0.1 eV. The former agrees quite accurately with references 6 , 10 . The later is one order lower than the activation energy of precipitation reported in reference 11 .