The Labour leader said a new law would allow family and friends of deceased men to seek the quashing of historical convictions for "gross indecency".
Legislation would be known as "Turing's Law" in memory of Alan Turing, he said.
The Enigma code-breaker was convicted of "gross indecency" in 1952 and was only given a posthumous pardon in 2013.
Homosexuality was illegal until it was decriminalised in England in 1967.
Mr Turing was convicted for gross indecency in 1952 in connection with an affair with a 19-year-old man, after which he was chemically castrated.
The conviction meant he lost his security clearance and had to stop the code-cracking work that had proved vital to the Allies in World War Two.
The mathematician was only given a royal pardon in 2013, nearly 60 years after his death by suicide in 1954. This followed an official apology by former prime minister Gordon Brown in 2009 for how Mr Turing had been treated.
Relatives of Mr Turing have led a high-profile campaign to secure pardons for the 49,000 other men convicted under historical indecency laws.
Announcing his support for the move, Mr Miliband said: "What was right for Alan Turing's family should be right for other families as well.
"The next Labour government will extend the right individuals already have to overturn convictions that society now see as grossly unfair to the relatives of those convicted who have passed away."
Asked whether David Cameron would back Mr Miliband's proposals, No 10 said the prime minister "will always continue to look carefully at what more can be done to right these wrongs".
A spokesman pointed out that the coalition government had already passed legislation to allow individuals with historical convictions or cautions for certain homosexual activities to apply for them to be removed from criminal records.
"It was this government that introduced that 2012 act," said the spokesman. "It was under this government that Mr Turing received the pardon through the use of the royal prerogative."
A pardon is only normally granted when the person is innocent of the offence and where a request has been made by someone with a vested interest such as a family member.
But, in Mr Turing's case, a pardon was issued without either requirement being met, after an intervention by Lord Chancellor Chris Grayling.

Whitton Primary School, near Knighton, opened in a village barn in 1724, before re-opening as a school house in 1767.
The closure is due to low numbers, and the cost per pupil being "significantly above the county average" Powys council said.
Residents objected to the closure of the 15-pupil school.
The council's cabinet approved the closure in July 2014, but following objections it was referred to Education Minister Huw Lewis, who upheld the decision.
Wealthy benefactor Dame Anna Child left her Â£500 fortune to build a school in the "village she loved" after she died in 1703.
"She wanted to provide a salary for someone to teach the children in the parish," said Graham Skipworth, chairman of governors for the school.
The school is funded by the local authority but is backed up by the Dame Anna Child's Endowed School Trust.
The trust raised money from the 147 acres (59 hectares) of farmland surrounding the school which it purchased three centuries ago.
Funds raised have been used to support staffing to improve teacher to child ratios, as well as purchasing extra computer suites for the classrooms.
Now it will now be used to provide parents of the children leaving with uniforms for their new schools.
A future Labour government would pave the way for posthumous pardons for gay men convicted under historical indecency laws, Ed Miliband has said.
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A Powys village school funded by an aristocrat for 291 years will close on Friday.