Spoiler..... or not.
Yes, Wangji know that Mo is Wei Wuxian. He know since the scene with Jiang Cheng because the music he used with the flaute is the same that wangji sang in the cave.
..... Sorry my bad english >_<
thanks , i watched anime but didnt read novel ^^
KxC:
Please read the novel, it is very good! Action, drama, tear jerker, comedy, mystery, etc...
To me the anime falls just a bit short as far as story telling goes. But u know scripts usually r not the same as the novel, the action is great and so is the background drawing, music too is good. But like i mentioned read the novel--i do not think u will regret it, it also helps explain quite a few things.
In the anime you can even hear the song that WWX played at the beginning is the same as the one LWJ sings in the cave :D (if you listen closely since self-made bamboo flute is sh*t xD)
*cough*... the one he got jealous of because he played it for Wen Ning?
Does Wan Zhan know his true identify or for him,''lunatic'' is just resembling Wei WuXian and that is why he has soft side for him? pls help ;_;