In a post on X on Sunday, Bukele asked that Venezuelan President Nicolas Maduro hand over 252 "of the political prisoners you are holding", under his proposed deal.
The Salvadoran leader did not say whether the prisoners would be incarcerated again upon an exchange.
Venezuela's chief prosecutor Tarek William Saab criticised Bukele's proposal and accused El Salvador of unlawfully detaining 252 Venezuelans.
In a statement, Saab demanded to know what crimes the detainees are accused of, whether they have appeared before a judge, have access to legal counsel, or have been allowed to contact family members.
Among those Bukele proposed for release from Venezuela were journalist Roland Carreno, human rights lawyer Rocio San Miguel and Corina Parisca de Machado, mother of Venezuelan opposition leader Maria Corina Machado, who he said is subjected to daily threats at her home.
He also mentioned nearly 50 detainees of other nationalities including US, German and French citizens, as part of the proposed exchange.
Adam Boehler, US special envoy for hostage response, praised the move in a post on X, and said that 10 Americans were among the 50 detainees proposed for the exchange.
Bukele said his foreign ministry would formally present the proposal to the Venezuelan government through diplomatic channels.
​In March, the administration of President Donald Trump deported at least 200 Venezuelans from the United States to El Salvador, accusing them of being members of the Tren de Aragua criminal gang.
The US is paying El Salvador $US6 million ($A9 million) to detain the migrants in its high-security Terrorism Confinement Center.
The Venezuelan government has said it has no political prisoners and that imprisoned people have been convicted of crimes. However, non-governmental organisations claim that more than 800 people are detained for political reasons.
The Venezuelan government has denied that the Venezuelans deported by the US have gang affiliations. Lawyers and family members of the detainees have also asserted that the migrants have no ties to criminal groups.
Saab described El Salvador's CECOT prison as "no longer a torture centre ... but a place of forced disappearance of innocent Venezuelan nationals."
He added he would formally request a full list of the detainees, their legal status, and medical reports for each one, and urged international organisations to call for their immediate release.
On Saturday, the US Supreme Court temporarily blocked the Trump administration from deporting another group of Venezuelan migrants accused of gang ties under a rarely used wartime law, issuing a stay after the American Civil Liberties Union (ACLU) asked the court to intervene on an emergency basis.
The Trump administration pressed the Supreme Court to reject the ACLU's request on the migrants' behalf, once they review the matter further.
White House officials said the president remains committed to his immigration crackdown, but gave no indication the administration would defy the court's decision.
