In the investigation,the fluidity of the Al-Mn alloy of different Mn contents is tested by a spiral perma- nent mould.Then,the solidification characteristic of the alloy is measured through the computer-aided cooling curve thermal analysis so as to reveal the inherent mechanism of the fluidity change.The results show that,when the Mn dosage increases from 0. 6% (mass fraction) to 2. 7%,the fluidity of the Al-Mn alloy tends to increase first and then decrease,and that the Al-Mn alloy is of the best fluidity when the Mn dosage is 2. 0% and the fluidity length reaches up to 88. 5% of commercial ADC12 alloy.Thermal analysis results show that there exist some laws in the changes of both the alloy solidification range and the difference between the pouring temperature and the den- drite coherency temperature with the Mn dosage,and the corresponding trend accords well with the change trend of the fluidity length.