One out of every six households received non-cash government benefits in 1981 through four means-tested programs, Medicaid, school lunches, food stamps and public housing, the Census Bureau reported yesterday.

The bureau said 14.5 million of the nation's 83.5 million households received benefits under one or more of these four programs, whose federal-state outlays will total about $55 billion in fiscal 1982, far outstripping the traditional cash welfare programs.

The number of beneficiary households was about 300,000 more than 1980, despite eligibility cutbacks engineered by President Reagan. This was partly because real cash income in the United States after adjustment for inflation was down, which made more people eligible for the programs.

The number of recipients of food stamps, subsidized housing and Medicaid increased, but the number of recipients of school lunch and child-nutrition benefits dropped slightly.

Only 47 percent, or 6.8 million, of the 14.5 million households receiving the non-cash benefits were below the government's official poverty line ($9,287 for a family of four). But a large portion of the 7.7 million above the poverty line who were receiving benefits were only slightly above it, in the category known as "near-poor."

Overall, the median household cash income of all those receiving these in-kind benefits was $8,025 in 1981, compared to $19,074 for the nation as a whole.

Officials say some of these 7.7 million were destitute when they got the benefits, then found jobs later and moved out of the poverty category.

Another reason people above the official poverty line sometimes get benefits is that Congress has deliberately set program cutoffs a little higher than poverty because these people, while not in poverty, are quite poor by ordinary standards. Still another reason is that many welfare clients would be discouraged from seeking work if they knew all welfare benefits would be lost once they crossed the poverty line.

The figures also show that while these non-cash benefits went to many households who were over the poverty line, 41.5 percent of all the households in the country below the poverty line got no Medicaid, food stamps or child-nutrition benefits whatever.

One reason is that childless couples and single people are ineligible for Medicaid, unless they are old or disabled, regardless of how low their income is. Another is that state income cutoffs for Medicaid eligibility are in many cases far below the poverty line. Still another is that people with a few thousand dollars in cash assets ($1,500 for food stamps) are ineligible even if they have no income at all.

Many of 14.5 million households received several benefits simultaneously: 471,000 received all four benefits, 2 million received three, 3.8 million received two and 8.3 million only one.

Blacks and female-headed households had far higher rates of benefit receipt than other households, reflecting their status as among the poorest groups in society. While only 6.1 percent of white households got food stamps and 7.9 percent Medicaid, the figures for blacks were 28.1 percent on food stamps, 28.3 percent Medicaid, and for female-headed families 30.6 percent on food stamps and 33.4 percent on Medicaid. The rates were triple that of whites for school lunches and housing.