Soybean cyst nematode (SCN, Heterodera glycines (I.)) is one of the most important soil-borne pathogens for soybeans.  In plant parasitic nematodes, including SCN, lysozyme plays important roles in the innate defense system.  In this study, two new lysozyme genes (Hg-lys1 and Hg-lys2) from SCN were cloned and characterized.  The in situ hybridization analyses indicated that the transcripts of both Hg-lys1 and Hg-lys2 accumulated in the intestine of SCN.  The qRT-PCR analyses showed that both Hg-lys1 and Hg-lys2 were upregulated after SCN second stage juveniles (J2s) were exposed to the Gram-positive bacteria Bacillus thuringiensis, Bacillus subtilis or Staphylococcus aureus.  Knockdown of the identified lysozyme genes by in vitro RNA interference caused a significant decrease in the survival rate of SCN.  All of the obtained results indicate that lysozyme is very important in the defense system and survival of SCN.