if the quantity of your shipment is small (such as small jumbo box) you can apply courier (like Tin Tin etc.) who have frequent service to Mainland China.
But if the quantity is big but not fill a conatiner (CY) you can apply forwarder (agent) to deliver the goods for you
Nearly all forwarders in HK can provide 一站式出口服務 shipping to China:
The following is a long list. But you only need to chat with a couple of them and they will tell you which company will best fit your requirements, in according to your goods category and freight sizes.