The process and theory of AZ31B magnesium alloy thin sheet incremental forming at elevated temperature was investigated by CNC machine, thermal stretch machine and metallographic microscope. The results showed that AZ31B alloy thin sheet at elevated temperature can be formed successfully by single point incremental forming. Forming limit angle increases with the increasing of temperature and initial thickness. The effect of anisotropy on AZ31B sheet incremental forming was the minimum at 250 ℃, and the quality of metal sheet was the main factor which can bring defects during the incremental forming. The technical parameters of AZ31B sheet incremental forming were as follows: initial thickness of thin sheet was 0.3~1.5 mm，the best forming temperature was 200~250 ℃, the amount of tool’s feed was 0.1~0.6 mm, the forming time was 25~30 min, and the incremental forming limiting angle was 50°~65°.
