Yea, it's an MMO named Queens Blade from Korea.

Trailer: http://news.mmosite.com/content/k/2011-11-25/queens_blade_1st_trailer_released_1.shtml

From the video, we can see several gorgeous female characters welding their weapons and fighting enemies tensely. It also showed that they could use some special skills to greatly increase attack power for an instant.

I bet there will be more male players than female palying the game. xD

I wanna to join in it

I thought that is what always what happened on MMO gamers and there is roughly 90% male gamers playing female characters to females playing female characters.