Here are two options I can recommend for the bus from humen to Guangzhou Airport:
1. THere is a city airport terminal on the first floor of Xinfeng Building in Humen Dadao. It has free shuttle bus to Dongguan Terminal. Dongguan Terminal has direct shuttle bus to Guangzhou Airport.
2. take bus at Humen bus Terminal to Tianhe Bus Station or Guangyuan Bus Station in Guangzhou. Both of these two bus stations has airport shuttle taking you to Guangzhou Airport.

Thank you Jerry,
Houjie - where I want to go in Dongguan, what will be ralilways station i have to go

Mr. Jerry, thank you, how to reach Houjie in Dongguan from your suggested train from Guangzhu Rialway Station. How far is the Guangzou Railways Station from Airport. How much will it cost to railways station from airport and then to Houjie in Dongguan.