Based on the bond operation mean-field approximation, the effects of bond alternation and single-ion anisotropy on an S=1 antiferromagnetic spin chain were discussed. The energy spectrums, free energy, static susceptibility and specific heat capacity were obtained by solving the self-consistent equations. The system can be transited from gapful to gapless which means the existence of quantum phase transition. The phase transition can be induced by bond alternation at $\alpha$=1.39 and anisotropy at D=−0.35 respectively. The critical points of these transitions are qualitatively consistent with the previous numerical results by other methods.