Abstract: Freshness is an important index for the measurement of egg’s quality and it is affected by different factors during storage. In this study，the grey relative degrees between the Haugh Unit and influencing factors of egg freshness were calculated based on the grey theory. And then，the importance of influencing factors was ranked according to the grey relative degree. Furthermore，the relations between Haugh Unit and these factors were analyzed theoretically. It was concluded that egg specific gravity was the first important influencing factor，while the egg freshness was affected by the eggshell strength most slightly. With the increase of storage time，the importance of egg-shaped index became weaken，but the egg weight factor was becoming more important. The results suggested that the grey theory presented in this paper might provide a new and effective way for comprehensive analysis of the relationship between egg freshness and influencing factors.

Key words: freshness, haugh unit, grey relative degree