Numerical simulation and experimental studies on cavity growth were carried out during the bulging process of superplastic magnesium Alloy. A three-dimensional rigidviscoplastic finite element program has been developed and applied to predict the cavity radiusand volume fraction of cavity growth. The final prediction on the cavity radius and volume fraction distribution was exhibited as colorful shade pictures. The experimental studies wereperformed under similar conditions to the numerical one and provided for quantitativecomparison. According to the metallography observation,the radius and volume fraction of cavity growth was quantitative achieved by using tive agreement with the experiment.