The present invention discloses a method and a device for generating a CNM, so as to improve a processing rate of a congestion problem. The method includes: monitoring a data volume of an output queue at a congestion point CP; monitoring a rate of a data stream corresponding to at least one congestion reaction point RP connected to the CP, and when the data volume of the output queue at the CP reaches a congestion threshold, obtaining identification information of a data stream that currently has a highest rate; generating a CNM for the data stream having the identification information, and sending the CNM to an RP corresponding to the identification information, so that the RP reduces, according to the CNM, the rate of the data stream corresponding to the RP.