You can take the direct shuttle bus from Tianjin Airport to Bawangfen Beijing. Then catch a taxi to the hotel. If you can not ctach it, you can take the airport shuttle bus to Tianjin Raiwlay Station. Then take the bullet train to Beijing South train station. From the south square of the station, you can get a taxi to the hotel.Taxi fare would be about 20-30 yuan.
For the accurated time and fare of the train, you can check China Train Tickets(https://www.travelchinaguide.com/china-trains/) .

thanks ms. faerygirl..

is it that transport are function when winter time? i'm so worried about that. coz i need to plan the transportation well. so what type of train i need to taken

Do not worry much about it. It does normally function in winter time.