Liu Xiaoming was speaking on BBC1's Andrew Marr Show the day before the start of President Xi Jinping's state visit to the UK.
He said the expected deal to build a new nuclear power plant at Hinkley Point was "in the best interests of Britain and also in the interest of partnership between China and UK".
"UK people want to have a better life, want to have clean energy," he said.
In a written answer to the Reuters news agency, President Xi said: "The UK has stated that it will be the Western country that is most open to China. This is a visionary and strategic choice that fully meets Britain's own long-term interest."
The Chinese ambassador was also asked whether a UK company would be allowed to build nuclear power plants in China in the way that Chinese firms will be doing in the UK.
"Do you have the money first, do you have the technology, do you have expertise?" Mr Liu replied.
"If you have all this, we certainly would want to have co-operation with you like the French. We have some co-operation with France."
The chief executive of France's EDF said on Sunday he expected an announcement about a deal with Chinese investors to build a nuclear plant at Hinkley Point, in Somerset, during the state visit.
"If all goes well, we will be able to announce major news in coming days; the first nuclear new-build in Europe since the Fukushima accident," Jean-Bernard Levy said.
The EDF chief defended the £92 per megawatt hour price that the UK government has guaranteed to pay his company.
"Britain is not giving guarantees to do us a favour, but because Hinkley Point will provide power 24 hours a day for 60 years. Security of supply has a value," he said.
Asked whether he expected the deal to be announced, Mr Liu said: "I certainly hope so because it is a very important project between our two countries."
The nuclear plant agreement is one of a number of business deals expected to be signed during the visit.
There is also likely to be a strategic alliance between BP and the state-owned China National Petroleum Corporation (CNPC) to develop oil resources in countries including Iraq.
It is reported that BP hopes to use the agreement to improve its chances of expanding its operations in China.
China's ambassador to the UK has said that the "UK needs Chinese investment".