BOISE, Idaho (AP) _ Somber Cabinet officials demanded the federal government's ''let-it-burn'' policy be revised after touring the fire-blackened West, and promised to send 1,200 Marines and other soldiers to help fight wildfires.

Interior Secretary Donald Hodel, Agriculture Secretary Richard Lyng, Deputy Defense Secretary William H. Taft IV and Idaho Gov. Cecil Andrus on Sunday toured the Boise Interagency Fire Center, which coordinates Western firefighting.

Earlier in the weekend the Cabinet members, sent to the West by President Reagan, inspected fire damage in Yellowstone National Park.

''The most important thing is to concentrate our efforts on getting these fires under control and then out,'' Hodel said Sunday. ''The old policy has to be reviewed and altered.''

The 16-year-old policy allows fires ignited naturally to burn within wilderness areas and national parks unless they endanger people or property. Wildfires on conventional national forest or rangelands are fought with available resources, he said.

In that time, 16,000 fires have burned a total of about 30,000 acres in the park, Hodel said. About 900,000 acres of Yellowstone have burned.

At Old Faithful geyser, Taft announced that two Marine battalions - 1,200 men, from Camp Pendleton, Calif., and two Army battalions would be dispatched to the firelines. The Pentagon has already sent 2,300 Army soldiers to help hard-pressed fire crews.

''So by the end of next week, we will see a doubled representation by the military in this effort,'' Taft said.

Some critics of the ''let-it-burn'' guidelines, including Sen. Malcolm Wallop, R-Wyo., have called for the resignation of National Park Service Director William Mott for adhering to the policy.

Rep. Richard Stallings, D-Idaho, has called for an ''immediate and sweeping'' re-evaluation by Congress of the Park Service's forest management.

''We need to emphasize that there are thousands of men and women on the fire lines who need our support,'' Hodel said. ''We've received some expressions that indicate the 'Monday morning quarterbacking' already going on is undercutting their morale.''

''The park is still there,'' Hodel said. ''There's a great deal of natural beauty and wonder still to see. We do have devastation to the vegetation, much of it along roadways where visitors will see it.''

Yellowstone has received a dusting of snow, slowing the spread of the blazes criss-crossing the park. But the interior secretary said forecasts of warmer weather this week could bring them back to life.

The Boise Interagency manages supplies and personnel for large fires involving overhead management teams. It has transported nearly 2.7 million pounds of equipment to the blazes this year with a total cost of about $15 million, said Sandi Sacher, BIFC fire information officer.

Some 68,490 fires have burned more than 4 million acres this year in the United States, including Alaska, said Boise Interagency Fire Center spokeswoman Sandi Sacher.

The Department of the Interior oversees the National Park Service and the Bureau of Land Management, while the Agriculture Department manages the Forest Service.