I solved this issue by other ways. Since the device I'm looking for is an IOMedia object. I found its BSD name by enumerating the kIOMediaClass object. And I looked up IOMedia's parent device to determine the USB device I'm interested in. CFStringRef mediaDevBsdName = NULL; mediaDevBsdName = (CFStringRef)IORegistryEntryCreateCFProperty(mediaDevice,                                                                  CFSTR(kIOBSDNameKey),                                                                  kCFAllocatorDefault,0); Hope this answer can help someone~