Lightweight thermal paper (LWTP) is a noteworthy import commodity with wide usage and large import value in the United States. In this study, the trade pattern and market dynamics of the LWTP import market in the U.S. has been examined based on almost ideal demand system. The results revealed that both the trade volume and import source of LWTP had changed during last decade. Competition relationships were found among major suppliers in both the short run and long run, and the long-run competition is stronger than that in the short run. The repeal of restriction on conducting countervailing investigation against non-market economy temporarily stimulated the import of LWTP products from China, but the following antidumping/countervailing investigation and the corresponding punitive duties generated trade depression effect on the imports. In addition, positive trade diversion effect was found on German products, which raises doubt on the effectiveness of this trade remedy policy.