The effects of Zn on the hot cracking tendency（HCT）of Mg-Zn binary alloys were analyzed according to the variation of cooling temperature

free contraction displacement and hindered shrinkage stress of the three Mg-Zn binary alloys（with 2%

6%and 10% Zn content

respectively）tested by the special designed equipment which could measure and record the subtle changes of temperature

displacement and stress during solidification process.The parameters for evaluating HCT including stress accumulating coefficient and its corresponding solid fraction range

and the maximum linear shrinkage percentage in free linear shrinkage process

were presented.The results indicate that the HCT of Mg-Zn binary alloy is decreased with the increase of Zn content below the maximum Zn solid solubility range

while the HCT of hypoeutectic Mg-10 Zn alloy exhibits the characteristic of cold crack with the Zn content exceeding its maximum solid solubility.