He works "on the night shift". Please don't ask me why! It is just one of those quirks of the english language, I'm afraid.

Hi Thuy Duong, We can simply write: "I am working the day shift." / "I worked the night shift last week." / "I clocked double shifts yesterday. I was so exhausted!" There isn't a need to use a preposition in this case. Hope this helps. Cheers, Lance