The author puts forward a warm incremental forming processing approach that is liquid supporting and heating in order to study forming limits of magnesium alloy sheets of different processing parameters. With ABAQUS software as the tool and mises stress and sheet thickness as research indicators, the author studies the influence of different temperatures, diameters and layer spacing on the forming limit and verifies through experiments. The result indicates that this approach is able to form AZ31B magnesium alloy sheet. In a certain temperature range, the higher the temperature, the smaller the layer spacing and the larger the forming limit angle Tool head diameter has a small impact on forming limit angle