"The paper discusses the effects of different means to extract the protein of eggs of Bombyx mori as well as to find the best conditions of SDS-PAGE to separate the proteins of eggs of B. mori. Trichloroacetic acid (TCA) precipitation, acetone precipitation and trichloroacetic acid-acetone (TCA-acetone) precipitation were used to extract the protein of eggs of B. mori. The protein was separated by different systems of homogeneous gel in a series of concentrations from 6% (separation gel) ~ 12%(spacer gel) to 6%(separation gel) ~ 15%(spacer gel) to search the most appropriate way of extracting the protein of eggs of B. mori and the conditions of electrophoresis. Protein maps of different homogeneous gel concentrations (6% ~ 12%, 6% ~ 15%) and different protein extractionmethods were obtained. Then the efficiency of the different maps was compared. It showed that removing the salt by TCA-acetone method and dissolving the protein by the lysis buffer consists of urea (9 mol·L-1)、CHAPS(4%)and DTT(1%) were the best way to ex-tract the proteins of eggs of B. mori. Meanwhile the suitable gradient of the homogeneous gel is 6% ~ 12%. The optimized method wasexplicated to analysis the differences between the eggs of the normal B. mori and whose infected by Nosema bombycis. Finally, the 66 kD protein band and 85 kD protein bands were gained and speculated to associate with the infection of Nosema bombycis."