Due to interdependencies among networks,cascading failure can spread from one network to others,which is a kind of relative failure based on function dependency by nature.A cascading failure model for interdependent networks is proposed after modeling two interdependent networks.Cascading failure in interdependent networks can be divided into internal cascading and cascading among networks.Degree-based cascading scale evaluation method is adopted to study the cascading failure phenomenon of two interdependent scale-free networks.It can be found that the bigger the average degree of the correlation rate and correlation nodes is,the more easily the cascading failure among networks occurs.The model can be extended to serve the turn for multiple cascade networks.