Embodiments of the present invention provide a path checking method, a sink node device, and a communications system. The path checking method includes: a sink node determines whether a check packet sent by an ingress node by using a check multicast tree is received within a predetermined time, where the sink node is a node connected to a receiver, the ingress node is a node connected to a multicast source, and the check multicast tree and a first multicast tree have a same transmission path and different multicast addresses; and if the sink node determines that no check packet sent by the ingress node by using the check multicast tree is received within the predetermined time, the sink node determines a path fault exists in an upstream node of the sink node in the first multicast tree.