Over the past six or seven years the states have massively cut back the real level of monthly welfare checks to the poor.

And they did it without provoking bitter fights or publicity because they did it largely by doing nothing.

Faced with the highest inflation in modern times, many states have simply left cash welfare benefits at the same dollar levels, or raised them so little that welfare families can buy far less than they once could.

The result is that "the most impoverished people in the nation are taking it on the chin," in the words of Scott Bunton of the National Governors Association.

Some states have begun trying to cut their rolls directly. The governor of Pennsylvania asked the legislature to chop 81,000 "employable" people off the state-funded general assistance program to save about $69 million a year. The state House has already complied and the state Senate is considering the proposal.

So far, only a few other states have cut welfare directly, but welfare experts fear this will become more prevalent if the nation's economic troubles continue.

The more common route is that followed by Texas, which has about $300,000 people receiving benefits under the Aid to Families with Dependent Children program.

In Texas, the maximum payment for a family of four without any other income has been $140 a month under the AFDC program since 1969, although a temporary bonus equal to another $5 a month was paid in 1979. An effort to raise the $140 to $187 a month failed last year in the Texas legislature, according to the office of the state welfare commissioner.

Since 1969, the nationwide cost of living has increased about 115 percent, so the $140-a-month basic payment for a family of four buys less than half what it bought in 1969.

New York City is another example. In 1975, the maximum AFDC payment in the city was $476 a month to a family of four without any other income, a fairly sizable benefit compared with other jurisdictions then.

But, as Sen. Daniel P. Moynihan (D-N.Y.) repeatedly points out, that $476 has not gone up a penny since then, while the cost-of-living index has jumped by about 46 percent. That $476, which enabled a mother with three children to get along with perhaps some degree of decency five years ago, can buy only two-thirds the food, clothing and shelter it bought then.

Some jurisdictions, like the District of Columbia, have substantially raised their welfare figures over the inflationary 1970s, but in few cases have they been able to raise them enough to keep pace with the cost of living.

Melone Broome, acting administrator of income maintenance programs for the District, said the maximum payment to a family of four without other income on AFDC here was $246.40 a month in 1973. It has been raised in steps and today is $348.73 for the same family, an increase of 41 percent. But in the same period the consumer price index shot up 78 percent.

The fact that states have failed to keep AFDC payments up with the cost of living is shown starkly in national figures computed by the Department of Health and Human Services (HHS).

Measured in terms of constant 1979 dollars, the average state maximum for a family of four without other income was $424 a month in 1973. By 1979, it had dropped to $349.

Add food stamps to the benefits a family of four receives, and their situation in three quarters of the states is still worse today than in 1973-74, according to a Health and Human Services calculation.

Again, measured in constant 1979 dollars, the real value of a family of four's maximum benefit plus food stamps was $523 a month in 1974 and $479 a month last September, according to a calculation of population weighted averages of state maximum payment schedules.

"Certainly, we have seen this inflation cutting back on the real value of AFDC," said Rudolph G. Penner, director of tax studies for the American Enterprise Institute.

Other federal programs for the poor have grown, like rental aid (more than $6 billion a year) and the cash payments for fuel assistant, estimated at about $1.8 to $1.9 billion a year.

But Dean Mitchell Ginsberg, of the Columbia School of Social Work, Assistant Secretary of HHS John Palmer and several other economists or welfare experts doubt that these added payments fully compensate most welfare clients fort loss of purchasing power, especially since they aren't evenly distributed throughout the welfare population.

One reason that the big U.S. outlays for food stamps (more than $9 billion a year), housing (more than $6 billion) and energy assistance ($1.8 billion) don't fill the deficit for all the AFDC and aged-blind-and-disabled (SSI) welfare clients is that large amounts go to other poor people not quite eligible for AFDC or SSI. Those at the lowest end of the scale, the direct welfare clients, don't get all this money.

Thus, people over the maximum income limits for welfare are eligible for food stamps, Medicaid, housing aid and fuel assistance and get a big portion of these outlays. And these benefits are also spread over a larger population with more unemployment than in 1973.

Only about a third of those living in subsidized housing for low-income people are on welfare, and only a little over half the households on food stamps are welfare clients.

Medicaid, the charity medical program, has also expanded greatly and is estimated at $25 billion, for fiscal 1980, three-fifths federally paid.

But welfare clients who are lucky enough not to get ill don't receive a penny from the program. And even for those who do, the outlays merely cover extra costs of sickness, and "they don't put food on the table or pay your rent," said Ken Bowler, a welfare expert on the staff of the House Ways and Means Committee. "You can't eat your crutches."

Even while the states have been saving large amounts by failing to keep welfare payment levels up to inflation, Bunton and welfare experts said, they have also kept the AFDC welfare rolls below what they would otherwise be by failing to increase dollar eligibility cutoffs.

Thus, using Texas as an extreme example again in 1969, only a family of four with an income of less than $187 a month was considered poor enough to be eligible for AFDC. Today, $187 buys less than half what it bought then, so theoretically the cutoff should be doubled so that familes of the same real poverty would be eligible. But it is still $187.

To a generally lesser degree, the same is true in many other states.

For the 4.2-million aged, blind and disabled, or SSI population, the over-all benefit-erosion isn't nearly as bad because the U.S. government makes the basic support payment and raises it annually to keep pace with inflation. But many states supplement the federal payment and, generally, their added cash payments haven't kept up with inflation.

As painful as all this is for the genuinely needy, Ginsberg fears it could get worse as states desperately seek out places to cut and prune to save money in tight times.

Already there are some signs he may be right. This year, Washington state and Michigan, relatively high-benefit states, are actually cutting the dollar amounts of supplements they pay to SSI clients.