The mercy appeals of Maulvi Abdus Salam, Hazrat Ali, Mujeebur Rehman and Sabeel alias Yahya were rejected by the President of Pakistan on November 20.
Gen Sharif signed the black warrants of the four convicts who were sentenced to death by special military court established after the school attack for speedy trial of militants, the army said in a statement.
After the signing of death warrants, there is no legal bar on the hangings of the convicts.
So far about 300 convicts have been hanged in the country, upsetting local and international human rights groups.