Traces of nanocrystals are introduced into Zr55Al10Ni5Cu30 bulk metallic glass through isothermally annealing the glass at 715 K for 30 min. The pre-annealed samples are rolled at different strain rates up to 95% thickness reduction at room temperature. The thermal stability and the free volume of the deformed sample are examined by differential scanning calorimetry. It is found that the thermal stability does not change with deformation degree. At any strain rate, free volume content increases continuously with the increase of deformation degree without saturation. As strain rate increases, however, the free volume content with the same deformation degree first increases and then decreases, which is significantly different from the case of the metallic glass with monolithic amorphous structure under plastic deformation.