The vote on Wednesday effectively squashes the last political attempt by Jewish settlers to stall the plan before the "disengagement" starts next month.
The defeat by a wide margin, though widely expected, dealt another blow to extremists whose hopes of reinforcing Gaza settlements with thousands of pullback opponents have been blocked by security forces in the desert outside the Gaza strip.
"We had additional proof today that the government, parliament, and the people too, support disengagement," Prime Minister Ariel Sharon told reporters.
Israel’s justice minister, Tzipi Livni, defending the mid-August start date, said: "Delaying the disengagement will ... extend the time in which Israeli society will tear itself apart more and more."
Sharon had delayed the start date by three weeks to avoid a Jewish mourning period. Israeli opponents had hoped a longer delay might allow time to derail the plan.
Most Israelis support the relocation of the 8500 Jewish settlers from the Gaza Strip and a few hundred of the more than 230,000 in the West Bank, but opponents do not want to give up any land seized in the 1967 Arab-Israeli war and which they see as God's gift to the Jewish people.
Palestinians welcome a withdrawal from any occupied land but point to the fact that Israel is strengthening its hold on settlements in the West Bank.
Camped in desert heat at a village near the Gaza Strip, thousands of Jewish protesters said the defeat in parliament made no difference to their campaign to march to the main Jewish settlement bloc and hamper the withdrawal.
"Delaying the disengagement will ... extend the time in which Israeli society will tear itself apart more and more"
Israel’s justice minister
They said they would try to set off at 7pm (1600 GMT), an hour later than originally planned.
To stop any possible breakout, police set coils of razor wire around the three-day-old encampment at the Jewish settlement of Kfar Maimon.
"We are calling on thousands of people to do their utmost to reach Kfar Maimon. This process will continue with the intention of reaching Gush Katif," said Jewish settler leader Benzi Lieberman.
Protesters shout slogans through
a fence at Kfar Maimon
But fatigue showed on some despite the carnival atmosphere provided by ultra-Orthodox rock music, ice cream sellers and the blaze of orange protest colour on shirts, hats and banners.
A steady trickle of people set off home. "I have to go back to my wife for the Sabbath (on Saturday)," said 26-year-old Yaakov Goldfield. "I hope to come back next week."