Previously,Stop service which controls virtual bridges.

sudo systemctl start libvirtd.service #Systemd OS

Then,take down the bridge.

sudo ifconfig virbr0 down #centos6 centos7
sudo 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

【Centos7】Delete virtual bridge