How can i go to yiwu train station from baiyun airport?

According to your arrival time, there is no direct long-distance bus. You are suggested to stay nearby the airport and start off in the next morning.
Take subway line 3 to Jiahe Wanggang Station and then transfer to line 2 to South Railway Station.
There are some bullet train to take you to Yiwu Railway Station. The schedules are 11:23, 13:35, 15:39 and 16:00.

i just managed to find the information for the train. there is one train T170 ( from GZ station 14:56 to yiwu station 05:58 - the trip around 15hrs and 2 minutes). is that correct? or should i go to south railway station better? thank you. and if i book a ticket for the train, must i pay by western union or i can just make booking then pay at the counter when i arrived? thank you.

Yes, that is correct. But this one is normal speed train.
You are still suggested to go to South Railway Station and take the bullet train. The duration is only 6 to 7 hours.
I'm not sure whether you can use the western union card. So you'd better prepare enough cash.
But you cannot book the ticket in advance and then pay for it when you arriving at the railway station.

Hi,you can go take taxi to GZ East Railway station and then take the ExPress train to Hangzhou .