Two of the radar-evading jets did a 60-second flypast at the Zhuhai air show in Guangdong province - the country's biggest meeting of plane makers and buyers.
Previously the jets had only been seen by bloggers.
The fighters are being seen as symbol of Beijing's desire to modernise and upgrade its military capabilities. President Xi Jinping wants to toughen China's armed forces as it takes a more assertive stance in the region, especially in the South China and East China seas.
The J-20 has been developed and made by the Chengdu Aircraft Industries Group, a subsidiary of Aviation Industry Corporation of China.
The Y-20, China's first heavy transporter jet has already been unveiled and will also be at the airshow.
The AG-600 seaplane is the largest seaplane in the world and likely to be used for search and rescue missions as well as patrolling China's seas.
A Xian H-6K bomber and the new Changhe Z-10K attack helicopter will also be at the show.
The new VT-4 main battle tank and Type 96B main battle tank have been sighted on their way to Zhuhai, where they will undoubtedly try to rack up export sales. Thailand has purchased 50 VT-4s for $4 million each.
SOURCES- BBC News, Popular Mechanics