The disclosure provides a controller, a method for adjusting packet flow rule, and a network communication system. The method includes: receiving, by a controller, a health status of a first port and a health status of a second port of each of a plurality of hosts in the network communication system; adjusting a packet flow rule of each of the hosts based on the health status of the first port and the health status of the second port of each of the hosts; and transmitting the adjusted packet flow rule of each of the hosts to each of the corresponding hosts to control each of the hosts to transceive a packet according to the corresponding packet flow rule.