Effects of mould temperature and pouring temperature on hot tearing and fluidity of AZ91D magnesium alloy were investigated.The results indicate that hot tearing resistance of the AZ91D alloy can be significantly improved with the increase of mould temperature.Hot tearing in the AZ91D magnesium alloy can not be observed with preheating temperature of 368℃ at different pouring temperatures.At a lower mould temperature（<268 ℃）,AZ91D alloy exhibits the desirable hot tearing resistance with pouring at 688℃.The influence of pouring temperature on hot tearing resistance is fade with the increase of mould temperature to be disappeared at mould temperature of 368 ℃.Both pouring temperature and mould temperature can obviously improve the fluidity of the AZ91D magnesium alloy,showing the remarkably role.At a lower mould temperature（68 ℃）,a little increase of mould temperature can only increase the fluidity slightly,while with pouring temperature at a higher level（718 ℃）,the effects of the increase of the pouring temperature on the improvement of the alloy’s fluidity can be neglected.In order to get better fluidity and hot tearing resistance,it is suggested for the production of AZ91D magnesium alloy components at a higher mould temperature（≥268 ℃） and suitable pouring temperature（688 718 ℃）.