Abstract: An improved method is proposed based on compressed b-i conjugate gradient （BCG） algorithm to perform efficient static and transient simulations for large-scale power and ground networks circuits.A more efficient compressed storage strategy is used to save the memory,and BCG algorithm is used to analysis the large-scale power and ground networks. Extensive experimental results show that the compressed BCG algorithm gain the significant memory and run-time advantages over the traditional approach and has more powerful capability to deal with the increasing size of power and ground networks.