Dynamic compressive performances of hot rolled AZ31B which have different angles between the compressive direction and the normal direction of the rolled sheet were tested using SHPB and strain control techniques. The mechanism of the plastic deformation at different strain amount was studied. Results indicate that when the strain rate is 1200 s-1, the twin number of samples in different orientation increases with plastic strain increasing; when the strain rate increases to 2800 s-1, the σ-ε curves have no obvious charges as the angle is 0o and 45o, compared with that at 1200 s-1; however the σ-ε curves vary from concave to convex when the angle is 90o, because thermal softening has occurred with increasing plastic strain, which results in the number of twin decreasing, and smaller strain hardening