This study investigates the formability of AZ31 magnesium alloy for bearing cover with inner cavity under hot forging. Firstly high speed metal test machine of China steel Co. Ltd. is used to carry out the compression tests under different forming temperatures and strain rates to obtain the stress-strain curves. Then, the stress-strain data obtained from compression test under different dies are applied to analyze the formability of magnesium alloy for bearing cover of the car under forging by commercial package DEFORM. Besides, hot forgings of magnesium alloy for bearing cover are carried out to study the formability of magnesium alloy, and to find the best forging condition. Meanwhile, from the measured result of hardness and metallographic observation of forged part, the influence of forming temperatures on the strength and microstructure of magnesium alloy under forging of bearing cover are evaluated. Finally, the Artificial Neural Network (ANN) is applied to learn the data obtained from experiments and to predict the experimental result under new combination of process parameters. Also, confirmatory experiment is carried out to prove the usefulness of the ANN model.