The president said it had failed to adequately respond to coronavirus because China has "total control" over the global organisation.
He said Chinese officials "ignored" their reporting obligations to the WHO and pressured the group to mislead the world when the virus was first discovered.
He noted that the US contributes about 450 million US dollars (£360 million) to the world body while China provides about 40 million dollars (£32 million).
The US is the largest source of financial support to the WHO and its exit is expected to significantly weaken the organisation.
President Trump said the US would be "redirecting" the money to "other worldwide and deserving urgent global public health needs", without providing specifics.
Mr Trump also announced that the United States will begin the process of withdrawing special trade benefits for Hong Kong because of the Chinese government's imposition of a new security law in the semi-autonomous city.
Tensions over Hong Kong have been increasing for more than a year as China has cracked down on protesters and sought to exert more control over the former British territory.
President Trump said the administration would begin eliminating the "full range" of agreements that had given Hong Kong a relationship with the US that mainland China lacked, including on trade and extradition.
He said the State Department would begin warning US citizens of the threat of surveillance and arrest when visiting the city.
The president also said the US would be suspending entry of certain Chinese citizens.
He did not provide specifics, but officials said this week that the administration was considering expelling thousands of Chinese graduate students enrolled at US universities.
Coronavirus: Everything you need to know