Disclosed is a multi-domain routing computation method, including: when it is determined that there are two or more domains deployed with a Path Computation Elements (PCE) in a network, a routing path is computed, between a PCE of a first domain and a PCE of a last domain among the two or more domains deployed with a PCE, using an extended Backward-Recursive PCE-Based Computation (BRPC) algorithm, and the routing path is computed using a Routing Controller (RC) in domains other than the two or more domains deployed with a PCE. Further disclosed are a multi-domain routing computation device, a path computation element and a routing network. The present disclosure can improve greatly optimality of path computation and has a fairly high efficiency for the path computation.