Guzman, a former university professor, now 72, reacted little as the sentence was delivered, as did the rest of the radical Maoist rebel leaders on trial with him.
His girlfriend and Shining Path comrade, Elena Iparraguirre, was also sentenced to life.
At a naval base outside of Lima, where Guzman has been imprisoned since 1992, judges took eight hours to read the lengthy sentence.
The 11 Shining Path leaders on trial with him received sentences of 24 to 35 years.
In 1992 Guzman was sentenced to life in prison for treason in a military court whose judges' identities were hidden. The sentence was overturned in 2005 by Peru's Constitutional Court, which ruled the secret military court did not guarantee a fair trial.
Guzman's new trial began one year ago. Civilian prosecutors this time sought a life sentence against Guzman, who led some 7,000 Shining Path fighters in a guerrilla war in the 1980s and 1990s.