The invention discloses a passive optical network architecture based on bandwidth multi-level convergence. The passive optical network architecture comprises a plurality of optical network units ONUssupporting one or more channels, multiple layers of optical line terminals OLTs supporting multichannel, a plurality of optical distribution networks ODNs for providing optical transmission channels for the optical line terminals OLTs and the optical network units ONUs, and a plurality of broadband remote access servers BRAS for connecting an access network and a broadband backbone network, the multiple layers of optical line terminals OLTs perform multi-level convergence on the broadband service to realize three-level convergence of the bandwidth service, thereby reducing the number of boardcards required for BRAS configuration of the broadband remote access server, reducing the consumption of fiber cores from the OLT to the BRAS and reducing the cost of the operator.