Effect of different melt temperatures, holding time, cooling rate and C2Cl6 degasser treatment on the density of Mg-6Zn-0.5Y alloy was studied. The experimental results indicated that the density of RPT samples decreased with increasing of melt temperature, which indicating that the hydrogen content increased with the increment of temperature. And the results also showed that the density of RPT samples rapidly decreased at first and then decreased slowly with increasing of holding time, suggesting that the hydrogen content rapidly increased at first and then reached a saturated state with increasing of holding time. When cooling rate increased, the density of ingots gradually increased at the same melt temperature. When the melt was treated by 1%, 3% and 5% C2Cl6 degasser at 720°C, the density of ingots gradually increased compared with the ingot without treatment by C2Cl6 degasser. The density of ingot reached the maximum value when C2Cl6 degasser content was 3%, i.e, the ingot density value increased from 1.8649g.cm-3 of the untreated sample to 1.8774g.cm-3 of the sample treated by 3% C2Cl6 degasser, indicating that 3% C2Cl6 degasser treatment has an optimum degassing effect.