Shipping to China from the USA can be achieved using any of the top carriers like the UPS, FedEx, DHL. However, we know more people who ship using DHL and USPS than any other. Shipping to China does involve cost. For example, a package from Atlanta to Beijing costs the following when packed in Flat rate boxes :
In my estimate this is the cheapest rate as compared to all other couriers. However, if you are looking for speed, then DHL cannot be beaten.
All the above carriers can be used for shipping from your Shopify store using the Multi Carrier Shipping label app.