The average summer (from June to August)air temperature is 1℃lower and zero-equilibrium line 88 m lower in the 18 years after 1968 than that in the 11 years before 1968 in the middle part of Qilian Mountains. It was found from the mass balance reconstructed according to the air temperature and precipitation from 1957 to 1985 on theJuly First Glacier that the glacier was characterized by the negative mass balance state with a cumulative negative mass balance value of 232.9 × 104m and by the possitive mass ba...