Tony Hogg, who was elected in November 2012, made the announcement on his website and said he was "proud of his achievements".
For the remaining eight months, he said his priorities included improving police funding for the force.
PCCs work to ensure police forces are running effectively and replaced police authorities.
The government insists they are not there to run local police forces but to hold them to account and respond to the needs of the public.
Mr Hogg told the BBC he would still be doing the job in his 70s if he was re-elected and he wanted to spend more time with his family.
It is a very big job and Tony Hogg has had a tough time with many members of the public being very sceptical over what he would achieve.
He has had to deal with cuts, cuts and more cuts. Since 2011, officer numbers in the force have fallen by about 400.
Looking ahead, he's facing more cuts. From talking to senior officers they expect the number of officers to fall below 3,000, in fact some say it is the minimum number Devon and Cornwall can be policed with and I think Mr Hogg has accepted he will not be able to maintain that number.
It is a very tough time to be a leader in this sector.

Jahed Choudhury, 24, married Sean Rogan at Walsall Register Office and shared his story on YouTube.
However, he told the Victoria Derbyshire Show he had been threatened online and in the street.
But the couple said they had also received messages of support and would continue to share their story.
Since their ceremony Mr Choudhury said the couple had received death threats online and abuse on the streets.
"The worst [messages] say 'the next time I see you in the streets, I'm going to throw acid in your face'.
"Even if I walk down the streets, I have people spitting on me and calling me pig - all the nasty stuff. I just keep walking."
The couple said they had not yet reported the incident to police and were considering whether to do so.
Mr Choudhury said he had also received "amazing" support from his online followers, including people who said the couple had inspired them to come out.
"I've been brought up Muslim and the Koran mentions you cannot be gay and Muslim. But this is how I have chosen to live my life. I will never get rid of my faith."
Mr Choudhury said he had attempted suicide in the past but added his family had been "really supportive" since he came out.
He has now set up a YouTube channel where his story received more than 5,000 views, and says he was motivated to speak out online to encourage support for gay people from religious backgrounds.
Devon and Cornwall's Police and Crime Commissioner (PCC) has announced he will not be seeking re-election in May.
[NEXT_CONCEPT]
A man thought to be one of the first UK Muslims to have a same-sex marriage said people have threatened to throw acid in his face since the ceremony.