Effects of hydrogen on the mechanical property and microstructure evolution are investigated on a Zr-based metallic glass composite contains both metallic glass matrix and body centered cubic (bcc) dendrite crystal. The compressive strength to failure descreased from 2.2 GPa to 1.9 GPa; the fracture strain decreased from 39% to 26%. The composite retains a moderate compressive strength and strain after hydrogenation. The composite shows certain resistance of hydrogen embrittlement. Neither nanocrystallization in amorphous matrix nor amorphization in bcc dendrite crystal is detected. But there are so many stacking faults in the bcc dendrite crystal after hydrogen charging. Hydrogen lowers the value of stacking fault energy and promotes planar slip of the dendrite crystal. Planar slip and slip localization accelerate the deformation of the dendrite crystal and lead to premature fracture of the composite. The experimental results are consistent with the hydrogen enhanced local plasticity mechanism of hydrogen embrittlement.