The influencing mechanism of different vibration frequencies on the filling and solidification mode and casting-mold gap was investigated in the filling and solidification process of AZ91 magnesium alloy. And the effect of mechanical vibration on heat transfer efficiency of the casting-mold interface was studied through independently designed heat transfer device. The results show that the mechanical vibration enhances the Reynolds number and reduces the thickness of laminar boundary layer during the filling process. It also destroys the initially solidified thin layer on the cavity wall, changes the solidification mode of magnesium alloy, refines the grains and changes the phase morphology and distribution. Finally, the vibration makes the casting-mold gap in a dynamic changing process after solidification and thus influences the heart-transfer of the casting-mold interface. Under vibration frequency of 0, 20 and 50 Hz, the mould’s highest temperature is 365.3, 372.1 and 377.1 °C, respectively, while the required time of mould reaching the maximum temperature is 111 s, 100 s and 91 s, respectively. With the vibration frequency changing from 0 Hz to 50 Hz, the mould’s maximum temperature increases gradually while the required time reduces