The decision was announced following president Mahinda Rajapaksa's bilateral talks with Xi.
"In appreciation of China-Sri Lanka friendship, the President announces reduction of fuel and electricity tariff effective tonight," President said in a Twitter message.
Rajapaksa said the per litre price of petrol would be reduced by 5 rupees while diesel would be reduced by rupees 3.
The biggest cut came in electricity tariff which would be reduced by 25 per cent, the President said.
The Norochcholai coal power plant, built with Chinese funding, would see adding of 600 mega watts of power to the national grid.
Slashing petroleum products prices and cutting electricity tariffs are widely seen by analysts as popular moves by the President, who is widely believed to be calling a snap election after November this year, to try and win his third successive term.