He quickly did his hair in the mirror before the interview.

did 是动词 do 的过去式，在这里表示"做、整理"的动作。 his 是代词 he 的所有格形式，意思是"他的"。 hair 是名词，指"头发"。 did his hair 是一个固定搭配，意思是"整理头发"或"做发型"。