A multidrop network system includes N network devices. The N network devices includes M transmission-permissible devices including a master device and at least one slave device, wherein M is not greater than N. Each transmission-permissible device has at least one identification code as its identification in the multidrop network system, and the M transmission-permissible devices have at least N identification codes. The M transmission-permissible devices obtain transmission opportunities in turn according to their respective identification codes in each round of data transmission. A K