This paper presents an efficient algorithm on P/G networks with mesh-tree topology in ASIC. The new algorithm combines equivalent circuit modeling and transmission-line modeling alternative direction implicit (TLM-ADI) methods to speedup the simulation of P/G networks with mesh-tree topology with linear time complexity. Specifically, it uses the equivalent circuit approach to suppress the mesh-tree P/G circuit into a mesh-only circuit in a linear and error-free manner. Then, it applies the TLM-ADI approach to linearly solve the reduced mesh-only circuit. Experiments show that our method indeed scales linearly to analyze P/G networks with mesh-tree topologies in ASIC with two orders of magnitude speedup over HSPICE.