Black Americans are worse off than they were a year ago and bearing "a disproportionate share of the hardships" from high unemployment and domestic spending cuts, the National Urban League said yesterday in its annual survey of the state of black America.

"Black America ended 1982 in worse shape than in 1981," said the report. "Two statistics are enough to tell the story. Black unemployment was 15.5 percent at the end of 1981. Black unemployment was 20 percent at the end of 1982."

The league called for a large new public-private jobs and training program aimed among other things at rebuilding "the decaying infrastructure of the nation." It also called for a halt to cuts in the food stamp, school lunch and other programs for the poor, plus more vigilant affirmative action and other civil rights enforcement.

Urban League President John E. Jacob, in an introduction, said 1982 "was not a good year, and of course, no year is, to be black and poor in America." The report placed much of the blame on the Reagan administration. Jacob also said the problems of blacks were not confined to the poor.

He deplored "what has happened to the black middle class, which is as it is in all societies, a bastion of strength and a source of motivation within black America." Only 30 percent of black U.S. families can be called middle class, compared with 56 percent of whites, and their position is "precarious," Jacob said, with few reserves to overcome "the bad years that are now upon them."

About one in three blacks lived below the official government poverty line, compared with one in 10 whites, the report said.

Some other major findings of the survey:

* Blacks, now totaling 26.5 million, are to some extent migrating back to the South and also to the West, and there has been some movement out of cities to suburbs, but they still cluster heavily in cities. This is especially true of the black poor.

* The 30 percent of black families that were middle class or well-to-do in 1980 (defined as having an annual income over $20,000) were up from the comparable 27 percent in 1970 but down from the 32 percent in 1979.

* About 42 percent of black households were female-headed in 1980, up from 30 percent in 1970. About 44 percent of black children under 18 lived in such families, double the 1970 figure.

* Black unemployment was 20 percent in October, 1982, and among teen-agers, 50 percent. Personal income was falling and living standards were declining, though largely among the 40 percent of families with the lowest incomes. Blacks generally earned about $59 for every $100 that whites earned from jobs.

* Blacks got 17.5 percent of their total income in 1980 from transfer payments, such as welfare, up from 12.6 percent a decade earlier.

* In March, 1981, only a third of black women 15 and over were married and living with husbands. Another third were never married, and the rest were separated, divorced or widowed. Half of female-headed households were poor, a slight improvement over 1969, and black women were the poorest of the major race-sex groups in society. But black women were moving significantly out of private household employment.

* Blacks in 1977 owned 231,203 of the nation's 14.7 million businesses, mostly small businesses and sole proprietorships, and had $8 billion (2 percent) of the $4 trillion gross receipts received by all businesses.

* Life expectancy for blacks in 1979 was 68.3 years to 74.4 years for whites; high unemployment and poverty tended to create depression and low self-esteem, resulting in high rates of alcoholism, drug abuse, suicide, mental illness, child-abuse and wife-abuse and crime. Five times as many black youths die from homicide per 100,000 population (42) as whites (8), and 46 percent of all people in prisons are blacks.

* Blacks are 12 percent of total population, but make up 33 percent of the Army, and within the Army have a high proportion of combat roles, where they learn few skills marketable in civilian life.

* In 1940 there were 45,000 black undergraduates in colleges, only 10 percent of them in non-black colleges.

By 1980, there were 926,700 and seven-tenths were in non-black colleges, but recent cuts in educational aid made further growth difficult, especially in private colleges.