They said the closing of the Freezing Point section of the China Youth Daily was a "historic incident" in a struggle between the Communist Party controls and calls for media freedom.
They said in a public letter signed on 2 February but issued on Tuesday: "History demonstrates that only a totalitarian system needs news censorship, out of the delusion that it can keep the public locked in ignorance."
Li Datong, the editor of Freezing Point, said that many of the signatories were officials under Zhao Ziyang and Hu Yaobang, the relatively liberal party chiefs overthrown in the 1980s, and they reflected growing discontent about censorship even among party veterans.
The signatories include Mao's secretary and biographer, Li Rui; an ex-editor-in-chief of the Communist Party's own mouthpiece, the People's Daily, Hu Jiwei; and a former propaganda boss, Zhu Houze.
They said China's elaborate restrictions on information could have dire consequences for China's political evolution.