We prepared 300 eggs from Isfahan Poultry farm industrial complex. All the eggs were fertilized and their average weight in the first turn was 61±2gr, in the second turn was 60±.5gr and in the third turn was 59.5±.5gr which was measured 6 hours after laying eggs. We were aimed at studying the effect of magnesium chlorate on the fetus chicken in preventing stress induced sound 6 weeks after birth.The eggs were divided into four groups and prepared magnesium chlorate with a concentration of 2.5 /100 ml. the first group contained of 25 eggs drilled in the air Sac with a small hole and 1cc of magnesium chlorate was injected and the hole was sealed with paraffin. The same procedure was performed for the second group in the 4^th embryonic age and in the two control groups. All groups were hatched in the days 21 and 22. The effect of sound was studied in all groups.our research demonstrated that the chickens who received magnesium chlorate during their embryonic stage had more resistance toward noise exposure.