下载并安装neocomplcache插件，然后在.vimrc中写入：

let g:neocomplcache_enable_at_startup = 1

let g:NeoComplCache_SmartCase = 1
let g:NeoComplCache_TagsAutoUpdate = 1
let g:NeoComplCache_EnableInfo = 1
let g:NeoComplCache_EnableCamelCaseCompletion = 1
let g:NeoComplCache_MinSyntaxLength = 3
let g:NeoComplCache_EnableSkipCompletion = 1
let g:NeoComplCache_SkipInputTime = '0.5'
let g:neocomplcache_dictionary_filetype_lists = {
    'default' : '',
    'text' : '/home/zzz/.vim/dict/dict.en'
    }

其中dict.en中包含10万多个英语单词。

效果如图：