Verdicts are not expected for several days or possibly weeks.
Few details of the allegations against Hu, the head of the company's iron ore business in China, and Wang Yong, Ge Minqiang, and Liu Caikui have been released.
The four men were formally arrested in August and have not been allowed to make any public comment.
Zhang Peihong, a defence lawyer for the four, said he expected the trial to finish as scheduled on Wednesday afternoon, adding that the verdict or sentencing could come much later.
Zhang and another lawyer, Tao Wuping, refused comment on the commercial secrets charges.
|Reporters and consular officials were barred from parts of the trial [EPA]
"It's too sensitive, beyond my capacity," said Zhang.
However, Tao said the business secrets allegedly stolen by the Rio Tinto employees were straightforward commercial information.
"The case is not as complicated as the public may think," he said.
On Monday, in the first day of hearings, the four executives pleaded guilty to charges of taking bribes, but defence lawyers said the amounts taken were far lower than the sums prosecutors allege.
The maximum penalty for commercial espionage is seven years in prison, while a bribery conviction could see them jailed for up to five years.
Almost all criminal cases that go to trial in China end in conviction.
The admissions of bribe-taking have been seen as a blow for Rio Tinto at a time when it seeking to restore good relations with China.
After initially staunchly defending its staff, the company recently urged the court to handle the case in a quick and transparent way.
Australian consular officials were allowed to attend the sessions of the trial involving the bribery charges, but the later sessions on commercial theft were conducted behind closed doors.
On Wednesday Stephen Smith, the Australian foreign minister, declined to comment when asked whether he was surprised by Hu's admission to bribery charges.
"I'm not proposing to be drawn on a commentary on the trial until the trial processes have completed," he told ABC radio in Canberra.
"Regrettably it [the end of hearing] also coincides with that part of the trial to which Australian officials don't have access to and we regret that and we've made that point clear to Chinese officials."
The case is seen by many working in China as a signal that the government is subjecting foreign companies to increasingly close scrutiny, raising the risks of running foul of secrecy laws that are themselves secret.
The four were arrested shortly after the collapse of tense iron-ore contract talks, and just weeks after Rio snubbed a major investment by state-run Chinalco.