To develop new topology with more powerful ability to tolerate node-failure in wireless sensor network

the existing research regards fault-tolerance topology as the multiply connected graph

and use the connectivity of the graph as standard to evaluate the tolerance ability.In this paper

we argue that fault tolerance of topologies is not equivalence to connectivity of the multiply connected graph by illustrating some practical examples

and point out the following three questions should be answered.First

what is node-failure tolerance of topologies? Second

how to evaluate this tolerance ability? Third

which type of topologies is more tolerant in node-failure? Then we define the concepts of node-failure tolerance and the degree of fault-tolerance and intrusion-tolerance.Then these concepts are used to evaluate the tolerance performance of hierarchy structure of wireless sensor network

and the conclusion is achieved that intrusion-tolerance degree is increasing with the ratio of cluster head increasing in hierarchy structure

but fault-tolerance degree decreasing.