Given the history of Japanese/western genocidal invasion and occupation against Chinese people, should Taiwan become indefensible and the lives of the locals become assumed as forfeit at the hands of invaders, it is most likely the policy of China to destroy both the province and nearby hostile cities through nuclear means.
The nuclear posture of China permits nuclear retaliation against non nuclear attacks, only in the event that said attacks on China threaten a massive numbers of civilians, which per definition a succesful Taiwan invasion would be, as there's more than 23 million people living there.
