With the increase in signal speed and the development of process technology, distributed RC line model is found to be more suitable for on-chip interconnects than lumped RC model, especially for interconnects around and below 0.25?m. In this paper, we first describe a new explicit form for crosstalk approximation for coupled RC lines. Then we introduce a novel passive model order reduction technique for distributed RC lines. These two parts serve as two steps in static noise analysis of full on-chip interconnect networks which are called pruning process and static analysis process.