Taiwan says a total of 39 Chinese military jets flew into its air defence zone on Saturday - the largest incursion by Beijing to date.
The defence ministry said the planes entered the area in two waves, during the day and during the evening, reports BBC.
It comes after 38 planes, including nuclear-capable bombers, entered the zone on Friday.
China sees democratic Taiwan as a breakaway province, but Taiwan sees itself as a sovereign state.
Taiwan has been complaining for more than a year about repeated missions by China's air force near the island.
"China has been wantonly engaged in military aggression, damaging regional peace," Taiwan Premier Su Tseng-chang told reporters on Saturday.
The government in Beijing - which is marking 72 years since the founding of the People's Republic of China - has so far made no public comment.
But it has previously said such flights were to protect its sovereignty and also targeted "collusion" between Taiwan and the US.
Taiwan's defence ministry said 20 Chinese aircraft came during the day on Saturday with a further 19 entering the area during the evening.
The People's Liberation Army (PLA) planes flew near the Pratas Islands atoll, the ministry said.
An air defence identification zone is an area outside of a country's territory and national airspace - but where foreign aircraft are still identified, monitored, and controlled in the interest of national security.
It is self-declared and technically remains international airspace.
A similar incident occurred on Friday with planes flying over waters between Taiwan and the Philippines.
Taiwan responded by scrambling its jets and deploying missile systems.
The ministry said the Chinese aircraft included four H-6 bombers, which can carry nuclear weapons, as well as an anti-submarine aircraft.
Beijing often launches such missions to express displeasure at comments made by Taiwan.