我使用的是Xubuntu 16.04， 把系统语言设置为中文之后update-grub之后发现开机的时候的引导项的中文都显示成了乱码，究其原因，发现以下文档中提到：
https://www.gnu.org/software/grub/manual/html_node/lang.html
13.1.12 lang
If this variable is set, it names the language code that the gettext command (see gettext) uses to translate strings. For example, French would be named as ‘fr’, and Simplified Chinese as ‘zh_CN’.
grub-mkconfig (see Simple configuration) will try to set a reasonable default for this variable based on the system locale.
https://www.gnu.org/software/grub/manual/html_node/gettext.html#gettext
14.3.16 gettext
Command: gettext string
Translate string into the current language.
The current language code is stored in the ‘lang’ variable in GRUB’s environment (see lang). Translation files in MO format are read from ‘locale_dir’ (see locale_dir), usually /boot/grub/locale.
而我发现我的/boot/grub/locale目录里面是空的，没有编码文件，恐怕这是问题原因，现在：
sudo gedit /etc/grub.d/00_header
把其中的grub_lang=echo $LANG | cut -d . -f 1 注释掉，
然后：
sudo update-grub
更新grub,
现在重新启动，看一下问题应该解决了！