Confusion and complaints marred the first day of a massive two-day federal food giveaway program yesterday in Prince George's County. So many people showed up at the 23 food distribution sites that six of them ran out of food and will have none today.

Part of the confusion resulted from eligibility requirements that are more strict than for previous giveaways. Many complaints came yesterday from persons over 65 or persons receiving Social Security disability benefits who came thinking they were qualified because they previously had gotten free dairy products under a different program.

The current nationwide food distribution program, mandated by a federal jobs bill enacted by Congress last spring, is primarily aimed at helping low-income and unemployed persons. Elderly persons have been primary targets of periodic cheese and butter distributions since December 1981, under an executive order by President Reagan.

Montgomery, Howard and Anne Arundel counties in Maryland also are giving away food this week, but not on the scale of the Prince George's program.

Officials of the Prince George's Department of Social Services, which supervised the distribution of 440,000 pounds of food--valued at $468,000--from surpluses provided by the U.S. Department of Agriculture, explained that to qualify for the free food, residents had to prove that they were currently a participant in one of five programs: welfare, food stamps, Medicaid, state unemployment or supplemental Social Security.

"I never had any problems before," said William Donaldson, 42, a Clinton resident who was angry at being turned away at the Clinton Christian Assembly Church. Donaldson is retired and receives a monthly Social Security disabilty check. He was eligible for the cheese giveaway in June, but not yesterday. "They're only giving it to people on welfare. . . they're discriminating against people and it's not fair," he complained.

But Cynthia Keith of Greenbelt wasn't complaining. She showed her Medicaid card and picked up a box of cheese, dried milk, rice and flour at the Greenbelt Town Hall. Keith said the food would last her and her infant daughter about four weeks. She said she had no problems dreaming up cheese recipes and said that while dry milk isn't very tasty, "it's good for any kind of baking and in my coffee."

"I ordered for 700 families , but I won't have enough for tomorrow. We'll give it out until it's gone," said an exasperated Helen Reed, who oversaw the distribution at the Glenarden Town Hall. She said there had been a line of people there steadily since early in the morning. She said that she too had to turn away several senior citizens and also caught a few "double dippers" who had picked up a box of supplies earlier in the day.

The doors at HELP in Laurel opened at 7:30 a.m. and by 10:30 a.m. Nicki Leonard, who was in charge at that center, had to close the doors and post sign telling people the supply had run out.

"It went fine and it went fast," Leonard said, adding that her center was able to give food to 150 families. She said planning will have to be improved before the next giveaway, scheduled for Dec. 14.

When the doors closed at 1:30 p.m. at Kent Baptist Church in Landover, some people who been waiting in the long line became irate and the county police were called to calm the crowd. Christine Felker, a spokesman for the Department of Social Services, said last night that there were tentative plans to shift some of the food from the larger centers to the some of the ones that had been forced to close.

There was a different problem at the Bladensburg Junior High School. Because the building is boarded up, there were no restrooms available until an emergency call was made for the delivery of "Jiffy Johns," according to Felker.

Yesterday, food went to eligible persons with last names beginning A through L; today the supplies go to persons with names beginning M through Z.

Part of the confusion yesterday was caused by uncertainty by many eligible recipients of the locations of the distribution centers. The following list shows the locations, with asterisks indicating that the site ran out of food yesterday and may not have any today:

Boulevard Heights Fire Station, 4101 Alton St., Capitol Heights; American Rescue Workers,* 716 Ritchie Rd., Capitol Heights; Surrey Square Apartments,* 6024 Surrey Square La., Forestville; Bowie Town Hall, 2614 Kenhill Dr.; Brandywine Fire Station, 14201 Brandywine Rd.; Capitol Heights Town Hall, 401 Capitol Heights Blvd.; Fairmount Heights Town Hall, 717 60th Pl.; Fire Station Company No. 20, Pratt St., Upper Marlboro; Glenarden Town Hall, 8600 Glenarden Pkwy.; Greenbelt Town Hall, 25 Crescent Rd.; HELP-Laurel Inc.*, 610 Main St., Laurel; Kent Baptist Church,* 700 Flagstaff St., Landover; Park 16 Apartments, 4800 Vermillion Ave., Oxon Hill; Seat Pleasant Town Hall, 6301 Addison Rd.; Whitehall Baptist Church,* 1205 Farmington Rd., Accokeek; Clinton Christian Assembly, 10506 Thift Rd., Clinton; Head Start (Oakcrest Elementary School), 929 Hill Rd., Landover; Sacred Hour Full Gospel Mission, 1022 58th Ave., Fairmount Heights; Victory Pentecostal Church, 6517 Highland Park Dr., Landover; Knights of Columbus,* 10140 Cherry Hill Rd., College Park; University Christian Church, 6800 Adelphi Rd., Hyattsville; Family Services, Brandywine; Bladensburg Junior High School, 4915 Annapolis Rd.