The melting level of hail is best estimated by level of the wet bulb temperature zero (WBZ). However, some misunderstanding exist among most weather forecasters in China, they think that hail’s melting level is the level of dry bulb temperature zero (DBZ). In this note, we try to explain why the melting level of hail is best estimated by level of the WBZ, and the dry air in mid troposphere can effectively lower the level of WBZ, being favorable for the hail falls.