Seeking nuclear materials that possess a high resistance against particle radiation damage is a long-standing issue. In this work, to reveal the radiation effect on the metallic glasses (MGs), the atomistic structural evolution of MGs induced by particle radiation is investigated, by performing a molecular dynamics simulation. It is found that radiation-induced vacancy-like defects appear in the MG structural model during the collision cascades. However, these defects are transient and unstable that they are fully annihilated. In particular, free volumes which are specific structural characteristics in MGs can annihilate these transient defects. In addition, there is a rearrangement of free volumes that large free volumes change into small ones and are apt to distribute homogeneously in the amorphous model after structural relaxation, so that the problems of radiation-induced structural instability and energy imbalance are solved. This work will shed light on evaluating the structural stability of MGs under particle radiation.