The Chinese embassy in Islamabad confirmed that Long had arrived at the mission and would soon travel back to China.
It was unclear whether a ransom had been paid or if Taliban fighters had been freed in exchange for Long's release.
The engineer was seized along with another Chinese colleague, their Pakistani driver and a guard near the Afghan border last August.
Pakistan's security forces recovered Long's colleagues seven weeks later after they escaped from the fighters while they were being shifted to a mountain hideout.
Attacks on foreign aid workers, company employees and diplomats have increased in Pakistan over the past year, especially in areas near the border with Afghanistan, where pro-Taliban fighters are battling government forces.
Earlier this month, a Polish geologist held by Taliban fighters was beheaded.
Two weeks ago, a US citizen heading the UN High Commission for Refugees (UNHCR) office in the southwestern province of Baluchistan was abducted and his driver shot dead.
A previously unknown group, calling itself the Baluchistan Liberation United Front, claimed it had seized the UN official and warned it would kill him if their demands were not met.