The decision came in response to numerous calls for the release of the political prisoners and is viewed as Bahraini monarch's latest bid to ignite talks to end a standoff with the opposition.
Twenty five Shia activists are among those released on Wednesday.
Bahraini authorities say they have released 308 prisoners, but according to Bahrain's Center for Human Rights, only 100 of them were political prisoners. Other 300 political prisoners are still in jail, the organization says.
Bahraini authorities have described the move as a gesture of goodwill. The political activists had been granted a royal pardon by King Hamad bin Isa al-Khalifa on Monday.
The political prisoners had been detained on charges of forming an illegal organization and disseminating misleading information.
Meanwhile, the Bahraini king went to Saudi Arabia on Wednesday to discuss the situation in his country with King Abdullah, who has just come back from the US after undergoing medical treatment.
Bahraini demonstrators maintain that they will hold their ground until their demands for freedom and a say in the government are met.
In the meantime, exiled leader of the opposition Haq movement, who had been scheduled to arrive from the United Kingdom to join Tuesday's demonstrations, has not returned home.
Hassan Mashaima had flown from London to Doha, Qatar, but then flew on to Beirut, Lebanon. It was not immediately clear what caused Mashaima to delay his return to the Persian Gulf country.
At least seven people have lost their lives and hundreds of others sustained injuries in the days of violent government crackdown on Bahrain's pro-democracy protesters.
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