The project, which cost $ 60,241, aims to restore the original look of the ancient prison and help people learn about Tibet's history, local officials said.
The prison is under repair for the second time since the decade-long turmoil of the "Cultural Revolution" launched by Chairman Mao Zedong which ended in 1976.
Losang Jigme, who is in charge of the project, said the reconstruction team will repair all walls, the roof of the three-story building, all nine cells of the prison, a court room and the prison control room.
Situated in Bargor Street of Lhasa, capital of the Tibet Autonomous Region, Langzisha is a typical example of Tibetan architecture covering an area of 720 square metres.
Built by the fifth Dalai Lama in the middle of the 17th century, it was originally meant to be the government headquarters of Lhasa, but was later turned into a prison.
The prison stored the tools for savage punishments, including the gouging out of eyes, cutting off of ears, hands and feet, pulling out of tendons and the skinning of people, the report said.
Due to long years of disrepair and humidity damage, some walls of the former prison are in the verge of collapse, said Losang.