Formula of mass transfer speed and diffusion flux was established during gas atom moving towards gas bubble by theoretically analyzing gas bubble growth in vertical centrifugal casting liquid metal.The results show that gas atom moving towards gas bubble can be divided into three stages.At the first stage

gas atoms diffuse from the inner of liquid metal towards the surface of gas bubble.Gas atoms transfer from solution to absorption and react into gas molecules in the absorptive layer at the second stages.Gas molecules diffuse into the gas bubble in the final stage.The mass transfer speed and diffusion flux of gas atoms diffusing into the gas bubble can be decreased with increasing in the centrifugal angular velocity and radius.In addition

a quantitative equation between the gas bubble radius and the centrifugal angular velocity as well as centrifugal radius is established for the gas bubble with the internal pressure equal to the external pressure.