作者：Bailm
链接：https://www.zhihu.com/question/27888608/answer/486347894
来源：知乎
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我也遇到了一样的问题, macOS 下的解决办法:

打开 terminal

查看U盘识别的磁盘号:

$ diskutil list
---
/dev/disk2 (external, physical):
   #:                       TYPE NAME                    SIZE       IDENTIFIER
   0:     Apple_partition_scheme                        *15.5 GB    disk2
   1:        Apple_partition_map                         4.1 KB     disk2s1
   2:                  Apple_HFS                         2.4 MB     disk2s2

完全擦除设备:

$ diskutil eraseDisk free EMPTY /dev/disk2
---
Started erase on disk2
Unmounting disk
Creating the partition map
Waiting for partitions to activate
Finished erase on disk2

格式化U盘:

$ diskutil eraseDisk ExFAT USB64 /dev/disk2
---
Started erase on disk2
Unmounting disk
Creating the partition map
Waiting for partitions to activate
Formatting disk2s2 as ExFAT with name USB64
Volume name      : USB64
Partition offset : 411648 sectors (210763776 bytes)
Volume size      : 29896704 sectors (15307112448 bytes)
Bytes per sector : 512
Bytes per cluster: 32768
FAT offset       : 2048 sectors (1048576 bytes)
# FAT sectors    : 4096
Number of FATs   : 1
Cluster offset   : 6144 sectors (3145728 bytes)
# Clusters       : 467040
Volume Serial #  : 5b908c10
Bitmap start     : 2
Bitmap file size : 58380
Upcase start     : 4
Upcase file size : 5836
Root start       : 5
Mounting disk
Finished erase on disk2

参考: Disk Utility cannot erase USB Drive