Mr. Chen was brought into the packed Taipei courtroom in handcuffs, the island's first ex-president ever to stand trial.
Mr. Chen faces allegations of looting a presidential fund, taking bribes and laundering money. He has pleaded not guilty and claims he is the victim of a political witch hunt.
Mr. Chen has accused his successor, President Ma Ying-jeou, of pursuing the case to appease China. Mr. Ma denies that accusation.
China reviled Mr. Chen because of his pro-independence stance.
During a pre-trial hearing, his defense attorneys claimed government lawyers tried to get witnesses to lie under oath to make false allegations against him.
Mr. Chen's wife, Wu Shu-chen, pleaded guilty to forgery and money-laundering at a pre-trial hearing on February 10th, but denied charges of embezzling money from the presidential fund.
Mr. Chen has acknowledged that his wife sent $20 million in excess campaign funds to overseas bank accounts.
Authorities suspect the funds were illicit. However, Taiwan law allows candidates to retain unused political donations.
Some information for this report was provided by AFP,
AP and Reuters.