Hi jamesyliu1210
Thank you for your request.
There are direct trains to Milano Centrale, they leave from Geneva Main station (Cornavin). Please note that work will be carried out on the lines in Italy, and the trains are being replaced by buses between Domodossola & Milano Centrale.
You will find the adapted timetable under the following link.
For more information, please contact our Railservice on +41 848 44 66 88 (CHF0.08/min.). If this number does not work, please try +41 51 225 78 00.
I wish you a good day.
Regards
NicolasK