In　this　paper,　we　show　that　the　dynamical　Casimir　effect　can　be　observed　in　a　hybrid　cavity　optomechanical　system.　By　introducing　a　two-level　atom　into　the　cavity,　the　atomic　transition　from　an　excited　state　to　the　ground　state　can　evoke　a　two-photon　process.　Our　proposal　does　not　require　a　driving　field　to　induce　the　dynamical　Casimir　effect,　which　is　very　alternative　to　previous　schemes.　Furthermore,　we　show　that　when　the　atom　is　replaced　by　an　identical　atomic　ensemble,　the　system　not　only　can　simulate　the　similar　dynamic　Casimir　effect,　but　also　exist　more　plentiful　physical　phenomena,　i.e.,　higher-order　resonance.　Numerical　simulation　confirms　the　validity　of　our　derivation.