By the investigation on different regions of the yolk of fertilized eggs, it was discovered that DNA and RNA were widely distributed in the yolk. DNA and RNA in the yolk were quantified by the method of fluorescence spectrophotometry with the reagents Hooechst33258 and RiboGreen respectively. The results indicated that DNA was uniformly distributed in the whole yolk(about 65.7 μg/L) and it was most probably that the DNA was contained in the yolk granules; while the distribution of RNA in the yolk showed another pattern: the amount of RNA in the superficial yolk beneath blastoderm was about 0.43 mg/L, which was much less than that of lateral yolk(2.87 mg/L) and vegetative pole(3.63 mg/L). The significance of the existance of yolk DNA and the unique distribution of yolk RNA remains to be elaborated.