BiG World Project v15.6 English.pdf and the manual in BGT-weidu 1.18 said BGT should install using 1.3.5512 verson Baldur's Gate: The Original Saga .But GOG released 1.3.5521 verson.Can I install BGT mod?Thanks for answer.

Which OS are you on?
The latest gog build only affected Mac (AFAIK) so if you're on windows, that'll be a 'yes, you can'
Should still be ok on other systems too but I can't say for 100%

国人就直说了，和操作系统无关啊，我问的是mod安装版本要1.3.5512，但GOG版本是1.3.55 21，不知道能不能装BGT-weidu

Yes you can. Many people, myself included, have used BGT with the GOG version of Baldur's Gate. It just requires to be patched to at least 1.3.5512. What you must understand is that BGT requires a completely clean -- no fixes, no mods -- version of Baldur's Gate 1.

OK,looks like I need to use BGTalesUS5512.exe to patch the game.And can't use 1.3.5521.Thanks

Why would you say that? No, you do not need to retro-patch the game -- you cannot do that anyway. I have already told you, you can install BGT with the GOG version (1.3.5521) of the game.

^What he said.

Also, you can install the BG2 fix-pack BEFORE installing BGT mod.

I see.I will try to install the mod.I just worry about "DO NOTinstall Baldurdash and DO NOTinstall theTOSC DirectX 8+ Patch! " in BiG World Project v15.6 English.pdf.
And"X. Changes in Version 1.3.5521

This version is updated for DirectX 8 and addresses the problem of
not being able to play a TCP game if you have DirectX 7 installed."

in 1.3.5521 readme.