Abstract: Protein-protein interactions play an important role in life.Analysis of the topology characters of PPI network composed of protein-protein interactions is one of the most important issues in the post-genomic era.This paper analyzes the topologies of 8 PPI networks of 7 species in DIP database by using complex network theory.Analysis shows that these PPI networks have small average path length and large clustering coefficients.The degree distributions of these networks follow a power law as given by p（k）=ak^-r（1<r<3，a≈1±0.5）.All these PPI networks are scale-free and idiosyncratic.All the PPI networks with average degree larger than 3.5 are robust against the random removal of not more than 10% nodes，but are vulnerable to the removal of 2% nodes of high degree.