Eight members of what Beijing labelled a "terrorist gang" carried out the stabbing spree at Kunming railway station in southwestern China, with four of them killed at the scene.
The remainder were formally arrested for crimes of "organizing, leading, taking part in a terrorist attack and intentional homicide," Yunnan provincial procuratorate said Saturday.
Three of those in police custody were captured two days after the attack, while a fourth, a wounded women, was held by police at the scene.
China has blamed separatists from its restive far-western region of Xinjiang -- home to the mainly Muslim Uighur minority -- for what it describes as an act of terror, with state media dubbing the incident "China's 9/11".
The four captives are expected to be sentenced to death, given that authorities in China appear to have already apportioned blame. Chinese courts are controlled by the ruling Communist Party.