He has a big/small mouth.（他有一张大/小的嘴巴） He has a round/square face.（他有一张圆/方的脸） 七年级对描写还不是很注重，只要用到形容词便行的。 你也可以在描写些，例如He wears a pair of glasses（他带着一副眼镜）这类的。 望采纳，谢谢。
My best friend is Xiao Ming. He has big black eyes, small nose, and also a small mouth on his little round face .He likes smiling,and when he smiles ,the dimples on his pink cheek make him lovely. 我最好的朋友叫小明.他有黑色的大眼睛,小小的鼻子,还有小小的嘴巴在他那小圆脸上. 他很喜欢笑.每当他笑时,粉色脸颊的酒窝可爱极了