which shuttle should i take from the Airport to reach the Hilton Tianhe,how long does it take

If by shuttle, you need to make a transfer. First, take shuttle bus line 8A to Guangyuan Coach Station, then change to city bus 175 to West Linhe Road Cross, then walk about 250 yards to the hotel. It takes abut 70 minutes.

Actually, there is an easier way for you. From the airport, take subway line 3 to East Railway Station, then walk southward along West Linhe Road, turn west at Linhe Xiheng Road to reach the hotel. The total walking distance is about 950 yards. The subway ride takes about 40 minutes.
If worrying about the long walking distance, you can use a cab to cover it. The cab fee is about CNY 10.