The safety checks will proceed until November to ensure nuclear facilities, nuclear equipment makers and uranium ore mines are free of safety hazards, the Ministry of Environmental Protection said in a statement.
The ministry asked firms to conduct self-examinations to "make sure nuclear facilities and equipment are safe and under control", the statement added.
Local environmental authorities have been asked to intensify safety checks, state-run Xinhua news agency reported.
The order for checks of nuclear facilities came after 173 people were killed in deadly blasts at a Tianjin warehouse storing hazardous chemicals.