The nation's $35.9 billion welfare system has become a confusing patchwork in which benefits vary ecormously from state to state and federal policies have tended to increase the disparities, according to an analysis by a national magazine.

Average benefits for each poor person in fiscal 1976 ranged from $370 in Wyoming to $3,033 in Hawaii, and benefits in the Northeast were about triple what they were in the South, said the survey, published in the Jan. 8 issue of National Journal.

The writers, Joel E. Havemann and Linda E. Demekovich, said the situation added up to a "mess" of major proportions; which President-elect Jimmy Carter has promised to clean up.

Carter and his advisers are reported to be considering two plans for welfare reform. One would guarantee a flat minimum income to families and persons earning less than an established national poverty level.

The second plan would give similar cash grants only to persons considered to be unemployable. It would concentrate on finding jobs for the 10 to 12 per cent of welfare beneficiaries who can work.

During the election campaign, Carter called on the federal government to assume responsibility gradually for the welfare system, to eliminate disparities and lighten the economic burden on state and local agencies.

In the five major welfare programs analyzed by National Journal, the federal government spent $22.1 billion and state and local agencies spent $13.8 billion in fiscal 1976.

Federal spending tends to widen regional differences in welfare benefits because it is often tied to the amount state and local governments contribute the National Journal said. State and local spending on welfare averages $1,422 per poor person in Massachusetts, but only $62 per poor person in Mississippi.

According to Bureau of the Census figures, the total number of people defined as poor declined substantially in the United States in the 1960s as the country went through a period of unprecedented prosperity.

But the National Journal estimates that there are still about 25.8 million poor Americans. (The Bureau considers as poor a non-farm family of four earning under $5,502.If the same family lived on a farm it would not be considered poor unless it earned about $500 less.)

The benefits for which these poor people can qualify differ widely from state to state.

Medicaid, the largest single welfare program, was enacted by Congress in 1965 to help poor people pay medical bills. But in Arizona, there are still no Medicaid benefits at all, because the state refuses to pay its share of the cost of medical services to welfare families.

Twenty-two states deny federally aided welfare money to families with children if there is a father capable of working living with the family. One such state is Virginia. However, the District of Columbia and Maryland both grant the welfare payments even if there is an unemployed father in the home.

But in Illinois, the benefits are denied unless one parent is dead, absent or mentally retarded, or unless the father is unemployed.

Federal "supplemental sucurity income" payments guarantee a minimum income for all elderly, blind and disabled persons regardless of the state in which they live. But there are disparities in this program as well, because some states supplement the federal grants while others do not.

As a region, the South trails far behind the rest of the country in acerage welfare benefits per poor person. The average was $784 in fiscal 1976, compared with the Midwest ($1,589), the West ($1,512) and the Northeast ($2,428). The District of Columbia treated as a state in the report study, ranks seventh in the nation in welfare spending per poor person with $2,016.

The National Journal article also noted that, in addition to the inequities in welfare payments, "seemingly endless red tape seperates many poor persons from the benefits to which they are legally entitled."