1. A method for updating a routing lookup tree, comprising: determining, by a Network Processor (NP), a layer update indication table and node update information according to updated entries, when determining that a routing lookup tree needs to be updated; and selecting, by the NP, in sequence a layer from the routing lookup tree as a current layer according to levels of layers, and if determining, by the NP, that the current layer needs to be updated according to the layer update indication table, then locking, by the NP, a previous layer of the current layer in the routing lookup tree, synchronizing, by the NP, the node update information to the current layer in the routing lookup tree, until determining, by the NP, that the current layer is a last layer needing to be updated according to the layer update indication table, and then ending, by the NP, the update of the routing lookup tree wherein, the locking means stopping the previous layer from sending a lookup key value to the current layer.