Lee Ching-yu was banned by Chinese officials from entering the mainland to visit her detained husband, Lee Ming-che.
The activist's wife was able to obtain a travel permit and was already set to leave Taiwan when she was notified by airline staff that her permit was canceled.
"I wonder why China needs to stop me, a defenseless woman, from visiting," Li told reporters at the airport.
Lee Ching-yu was going to China to visit her husband whom she has not seen since March 19.
Prior to her visit, a middleman from the Chinese intelligence went to her and asked her to be "obedient and quietly cooperative."
The middleman is former Taiwanese intelligence officer Lee Chun-min, who threatened Lee that if she fails to cooperate, the Chinese government will release videos of a confession from her husband.
The former intelligence officer was also trying to convince Lee Ching-yu to keep a low profile so that her husband will be released immediately.
Lee Ming-che was arrested by Chinese officials in Macau because he was deemed as a threat to national security.
Lee Ming-che was in Macau last month to attend a meeting when he went suddenly missing. He has been very vocal about China-Taiwan relations on WeChat.
Lee Ming-che is also a strong supporter of Taiwan's independence from China.
A representative from the Taiwanese Affairs Office, Ma Xiaoguang, said, "Regarding Lee Ming-che's case because he is suspected of pursuing activities harmful to national security, the investigation into him is being handled in line with legal procedures."
The disappearance of the activist had caused anxiety and panic among his family and friends, according to the Democratic Progressive Party (DPP). Lee was a member of the party.
Lee Ching-che and many other foreign nationals who have shown criticism to China's policies are being detained. The government releases videos of them confessing to undermining the government.
The detainees later recant their testimonies after release.