In order to provide with fundamental data of the wrought Mg alloy for press forging, the effect of annealing temperature on the microstructure, texture development and tensile properties is studied in a commercial AZ31B Mg alloy sheet. Basal texture i.e. $(0001){pm}5^{circ}$[21$ar{3}$0] is developed in a commercial AZ31B Mg sheet, and the texture is not changed considerably by annealing over $400^{circ}C{ imes}30min$, while (10$ar{3}$0) component with high intensity can be observed due to abnormal grain growth. When the sheet is tensile-deformed with RD, $45^{circ}$ and TD directions at room temperature, fracture strains are given by 25.8, 21.4 and 11.9% in the order of RD, $45^{circ}$ and TD directions, respectively. With increasing annealing temperature up to $450^{circ}C{ imes}30min$, little change in mean grain size can be revealed by annealing below $300^{circ}C{ imes}30min$ but an abnormal grain growth, where some grains become significantly coarser than the rest, occurs by annealing above $400^{circ}C{ imes}30min$. The maximum tensile strain of around 25% is obtained by annealing below $300^{circ}C{ imes}30min$, but it is abruptly decreased to 16% by annealing above $400^{circ}C{ imes}30min$ owing to intergranular fracture of abnormal grown grains.