Previously,Stop service which controls virtual bridges.

sudo systemctl stop libvirtd.service #Systemd OS

Then,take down the bridge.

sudo ifconfig virbr0 down #centos6 centos7sudo ip link set dev virbr0 down #centos7

Finally,remove this bridge.

sudo brctl delbr virbr0

Additionally. If libvirtd.service is restarted. the bridge will created automatically. So you better disable this service.

sudo systemctl disable libvirtd.service