Both can be used.

The nutrients and effects of fresh and dried mugwort leaves are almost the same, generally fresh mugwort leaves contain more water and volatiles, and at the same time, they have more aromatic odor, so the eggs boiled with fresh mugwort leaves will smell more fragrant. But fresh mugwort leaves are not available all year round, most of the time is the use of dry mugwort leaves is more common, dry mugwort leaves can also be better volatile efficacy, boiled out of the egg efficacy is better, so mugwort boiled eggs with fresh or dry mugwort leaves are available.