The present invention relates to the field of optical communication and provides a method and system for arranging link resource fragments. The method comprises: configuring cascade services in a link in advance; generating a preset arrangement method according to an initial channel number of occupied channel(s) in the link and a cascade number of service born in the channel(s) (S210); a local end node that initiates a link resource arrangement notifying an opposite end node to arrange link resource fragments (S220); the local end node and the opposite end node reconfiguring a cross connection according to the preset arrangement method (S230). The method and system of the present invention can re-arrange the channel resources within one link, and integrate the scattered channel resource fragments into complete and available resources with a broader bandwidth, thus achieving the maximum utilization of the link bandwidth resources.