Boris Johnson says the Carrier Strike Group (CSG) 21 deployment will project Britain's military "hard power", as well as the country's values.
He said: "The people who will be going on this mission will be doing a number of things.
"They'll be projecting not just Britain's hard power – our military capabilities which are obviously extraordinary – but also our soft power: our values, what we stand for, our belief in democracy, in the rule of law."
The 65,000-tonne warship had been scheduled to leave Portsmouth on Sunday morning, but the prospect of heavy winds prompted the Navy to change plans.
It will be the first time the carrier has left the Hampshire port at night, although it has sailed into Portsmouth in the early hours previously.
Part of the fleet's route will take it through the disputed South China Sea.
Mr Johnson said: "One of the things we will be doing clearly is showing to our friends in China that we believe in the international law of the sea, and in a confident, but not confrontational way, we will be vindicating that point.
"We don’t want to antagonise anybody, but we do think that the United Kingdom plays a very important role, with friends and partners – the Americans, the Dutch, the Australians, the Indians, many, many others – in upholding the rule of law, the international rules-based system on which we all depend, and that’s one of the many things that this Carrier Strike Group will be doing."
HMS Queen Elizabeth, with eight RAF and 10 US Marine Corps F35B stealth fighter jets on board, will depart for Asia accompanied by six British military ships, a submarine, 14 naval helicopters and a company of Royal Marines.
A total of 3,700 sailors, aviators and marines are involved in the deployment which will cover 25,000 nautical miles.