Abstract: Protein changes in the eggs of Ostrinia f urnacalis parasitized by egg parasitoid ,Trichogramma ostriniae , were studied by SDS2PAGE. The results showed that the changes took place 48h after parasitization. The quantity of 97 kD protein both in parasitized and unparasitized eggs decreased significantly after 60 h. The 90 kD protein appeared in the parasitized eggs at 48 h and its quantity mincreased at 60 h. The quantity of 50 and 44 kD proteins both in parasitized and unparasitized eggs decreased after 84 h , in particular in unparasitized eggs. The number of protein bands that migrated tothe similar distances in parasitized and unparasitized eggs with similar development time was about half of the total number of protein bands in parasitized and unparasitized eggs at any developmental stages , except for 72 h and 96 h. There were about 4 fewer or more protein bands in parasitized eggs than in unparasitized eggs at any developmental stages except for 6 h , when there were 9 more protein bands in parasitized eggs than in unparasitized eggs. The special protein responsible for defence and anti-defense during parasitization maybe occur at this stage.