AZ31B magnesium alloy ingots were prepared by spraying water towards the bottom ingot and holding at side face of the ingot using a heating-furnace.The solidification structure of magnesium alloy was modified through changing the melt superheating temperature

and effects of grain size and shape on ambient mechanical properties of AZ31B magnesium alloy were analyzed.The results show that the columnar crystals are generated at the bottom and the equiaxed crystal is at other location of ingot prepared using the method.Meanwhile

the structure exhibits dense with absence of shrinkage porosities（holes）.With melt superheating temperature increased from 720℃to 900℃

the length and spacing of columnar crystals are decreased from 0.8mm to 0.1mm

and from 0.7mm to 0.2mm

respectively.The equiaxed crystal size is decreased from 0.8mm to 0.1mm at 130mm position apart from the ingot bottom.The ambient tensile strength and plasticity are improved with decreasing in the equiaxed crystal size

especially for the plasticity.When the tension direction is perpendicular to the axial direction of columnar crystals

the tensile strength and elongation of the samples are obviously decreased compared with the equiaxed crystal.The ambient compression properties of magnesium alloy are increased with the decrease of the columnar crystal spacing.Under the same columnar crystal spacing conditions

the compression properties of perpendicular to columnar crystal axial direction are better than that of parallel to columnar crystal axial direction.