Why Donald Trump hates China?

Trump believes that the Chinese manipulate their currencies to sell more goods. He promised, in one of his speeches, to force a 45% import tax on their goods.

In many of his speeches Trump mentioned that china has waged an Economic war against the united states which resulted in ripping the united states off.

Trump doesn't like the fact that the US has a trade deficit with China of $500 billion a year. He wants to change that. 

Donald Trump said in one of his speeches that the US is not getting a fair treatment from China as they don't respect economic treaties.

Trump said that the US is so dependent on China and he doesn't like that. 

Trump said in one interview that he knows that China can solve the North Korea problem and that without them North Korea won't have food to eat. He thinks China is being manipulative by saying that they can't convince the Koreans to do what they want.

In one of his speeches Trump said that Afghanistan is very rich in minerals and while the US is losing men, China is collecting those minerals from the other side of the mountain.

Trump believes that as a result of China's trade practices they are actually killing many of the american companies and ruining the US economy. (See Why did China devalue its currency in August 2015?)

Trump said that the US has lost between 4 and 7 million jobs because of Chinese practices. He was referring to how Chinese companies flood the US with cheap products.

Some people suggest that Trump's feelings towards China result from the belief that they are a big military threat.

The fact that China is rising fast has made them the biggest competitor to the US in many fields. Trump wants to restore US leadership again. (See Why do some people want to migrate to the United States?)