Hello, I'll travel to Taiwan on 20/3, please advice on which type clothing should I wear.

As the average temperature shall be around 21℃ during that time, I suggest you take along relatively thick T-shirt, jacket and jeans! If you will go to Taipei or Taichung, there might be a little rainfall, so you may need to prepare an umbrella; if you will head for Tainan, it will be sunny on that day!