The politicians are alleged to have received bribes a year ago from the then opposition leader, Moana Carcasses, who is now deputy prime minister.
Moana Carcasses was allegedly trying to procure the MPs support before a planned vote of no confidence to remove the then prime minister Jo Natuman.
It is alleged that US$319,000 was involved.
Radio New Zealand International's Vanuatu correspondent, Hilaire Bule, says it is the first bribery case involving the country's leaders and about a hundred people are observing the trial in Port Vila.