We already have Tariffs on many things coming from China. And, from other places as well. It's not always a good idea to listen to a candidate... especially an insurgent candidate.... who spouts stuff that we like. What they say isn't always accurate. It's always a good thing to check stuff out.
Since GATT, tariffs on Chinese and most other foreign manufactured goods have been low, and GATT caps the amount by which these can be raised in the future. The real question is whether Trump or any other candidate can renege on GATT.