Abstract: Freshness is a key quality attribute of egg, which can be quickly and non-destructively detected by studying the correlation between freshness and morphological characteristics of egg content. Egg images were obtained by using machine vision device, and egg freshness (Haugh unit) can be acquired through the test. Egg yolk and air room appeared after effective image processing was done. The pixel area ratio of yolk to the whole egg, the ratio of air room height to major axis length were selected as characteristic parameters, and the correlations between the two parameters and freshness were developed, and test results show that the correct rates to distinguish freshness are 91% and 93%, respectively by the correlations. The findings indicate that the two ratios increase with the decrease of egg freshness.