STUTTGART, West Germany (AP) _ The first of 3,500 Wisconsin National Guard troops arrived Saturday in Stuttgart to prepare for field manuevers in West Germany, a U.S. Army spokeswoman said.

Spokeswoman Maj. Donna Reed said a C-141 military transport plane arrived Saturday morning with 125 members of the 132nd Combat Support Battlion.

''Another C-141 arrived several hours later in pouring rain,'' carrying 90 members of the 121st Infantry Battalion, Reed said.

Both groups are from subordinate units of the Wisconsin National Guard's 32nd Separate Infantry Brigade (Mechanized), which is headquartered in Milwaukee, Reed said.

U.S. Army officials said this week transfer of 3,500 troops from the 32nd Separate Infantry Brigade to West Germany would be the largest such movement ever of a single U.S. reserve or National Guard unit during a ''Reforger'' exercise.

Reforger, an acronym for Return of Forces to Germany, is an annual exercise in which American troops and equipment are brought to Europe to reinforce NATO forces assigned to defend the continent against Soviet-led Warsaw pact troops in case of war.

This year's Reforger is the 18th in the series and the second consecutive in wintertime.

Reed told The Associated Press by telephone the troops Saturday were quickly processed through Stuttgart airport. ''Within 90 minutes the first group was on its way,'' she said.

From Stuttgart the troops were to go by truck to the Grafenwoehr military training area in the northeast of Bavaria, where they will set up for NATO winter maneuvers, called ''Certain Sentinel 86,'' Reed said.

The U.S. troops will join Europe-based units of the 7th and 5th U.S. Army Corps, Canada's 4th Mechanized Brigade Group, and the West German 12th Panzer Division, Border Police and Territorial Defense units in the Jan. 20-31 maneuvers near Nuremberg.

Ms. Reed said the troops appeared to be in good spirits after the long flight from the United States.

She quoted Spec. 4 Patrick Wilson of Lake Geneva, Wis., as saying: ''It's great to be here, so far everything is going smoothly.''

According to U.S. Army spokeswoman Barbara Filbert of the 21st Support Command in Kaiserslautern, more than 3,900 active duty, reserve and national guard soldiers were due to arrive at bases in Western Europe Saturday.

The 21st Support Command, in southwestern West Germany, is responsible for feeding, housing and issuing equipment to incoming Reforger troops.

''Since Monday 6,781 soldiers have arrived from the United States,'' Ms. Filbert told the AP on Saturday. ''By the end of next week more than 20,000 will have been brought over.''

Elements of U.S.-based units arriving during Reforger include troops of the 53rd Signal Group from Tallahassee, Fla., the 18th Field Artillery of Ft. Sill, Okla., the 91st Transportation Detachment of Hampton, Va., and the 1st Infantry Division of Ft. Riley, Kansas, and others, Filbert said.

A sea transport ship, the Callaghan, has docked at Zeebrugge in the Netherlands, bringing part of the 300,000 tons of military equipment that will be transported to West Germany by rail and truck for the winter maneuvers, Ms. Filbert said.

She said three other ships were scheduled to arrive with more equipment and troops at Antwerp, Belgium within a week.