Park faces multiple charges including bribery, coercion and abuse of power for offering governmental favours to tycoons, and is being held in custody.
She was impeached by parliament after months of mass protests against her over a sprawling graft scandal, and the constitutional court upheld the decision in March, dismissing her from office. She went on criminal trial in May.
The warrant for Park's detention was extended for six months last week, with the court citing the risk that she could destroy evidence if released.
The lawyers protested at the extension of the warrant, saying that the principle of the presumption of innocence was "collapsing", according to Yonhap news agency.
More From This Section
"As we've reached a conclusion that any defence argument for the defendant is meaningless, all of us decided to resign," one of them, Yoo Yeong-Ha, told the court.
The court asked them to reconsider since the proceedings cannot continue without defence lawyers.
State attorneys will be appointed to defend Park if her own lawyers insist on withdrawing, but the replacement will take time as new representatives would have to review more than 100,000 pages of evidence.
The past six months had been a "horrible and miserable time", during which she had "endured pain in my body and mind".
Park arrived at the courthouse in handcuffs and looking drawn. But she insisted she was innocent.
"I never accepted or granted requests for favours while in office," she said. "I believe it has been fully revealed during the course of the trial that the corresponding suspicions are not true."
Park, the daughter of late dictator Park Chung-Hee, is the third former South Korean president to be accused of corruption in Asia's fourth-largest economy, where politics and big business have long been closely tied.
Two former army-backed leaders who ruled in the 1980s and 1990s -- Chun Doo-Hwan and Roh Tae-Woo -- both served jail terms for charges including bribery after they retired.