Are you thinking of writing a fanfic Earth? It all depends where the Chinese were set down. For instance, if they landed in the Shire they would prospor and have ready available servants in the hobits. Whereas, if they were to alight in the barren East, they would take longer to find a way to move on the free people in order to secure valuable resources. If they were in the East, Sauron would either obliterate them seeing them as a threat or ally with them, I tend to lean towards the latter. For, Sauron would take any advantage he could to quash the freedom of those opposing him and if the Chinese had the same idea, then he would find very valuable allies.