1. new download of sublime text 3: 3083, windows 64bit portable version.
2. not install any package(Data\Packages\User and Data\Installed Packages is empty)
3. use it open a 27M txt file, it take about 6 minute.
4. i check the file, it contain a very long line, about 25M bytes. it maybe the reason, but UltraEdit can quick open and edit it, i want use sublime to be my only editor, not need another

the board attachment quota has been reached. I can’t upload a sample.

Can you try to disable ligne wrap ?
I observed that it makes sublime laggy on really long lines.

i tried
“word_wrap”: “false”,

but still very slow

normally i would recommend using BBEdit, it is very fast for opening large files (also for regex and grep across many files/directories).

however, as you are on windows, i can only suggest trying Atom. it was also slow a few months ago, but many updates come out (daily) and it has been getting, and will likely continue to get, much faster.