Abstract: Objective To observe the DNA damage effect of cadmium on hominine malignanthepatocar inoma SMMC-7721 cell line,and to discuss the application of CASP softw are in analysis of single cell gel electro phoresis(SCGE)results.Methods SCGE assay was per for med to detect the DNA damage of different concentrations of CdCl₂ on SMMC-7721 cells.Traditional method was used to analyze the gel electrophoresis results and damage rate was calculated;Meanwhile,CASP software was applied to compute six indexes including per centage of head DNA(HDNA%),percentage of tail DNA(TDNA%),tail length(TL),comet length(CL),tail moment(TM)and oliver tail moment(OTM).Results 24h after adding with CdCl₂ on SMMC-7721,comettails of hepatocarcinoma cells of 5,10,20 μmol/L were increased,leading to the aggravation of DNA damage;DNA damag erates were increased and there were significant differences between ex posure groups and control group(P<0.05).HDNA% value decreased and TDNA% increased,TLCL,TM and OTM values were all ascended suggesting more severe DNA damage.There are statistically differences in DNA damage between exposure and negative control groups(P<0.05).Conclusion Cadmium could induce DNA damage of hominine malignanthepatocarcinoma SMMC-7721 cell.The analysis results of the two methods are coincidence.And CASP softw are could analyze SCGE results synthetically and produce more scientific and reliable conclusions.