Less than two-fifths of the nation's jobless workers are getting unemployment insurance benefits even though unemployment is still close to its highest level since World War II, according to Labor Department figures.

In July, the latest month for which figures are available, only 4,133,956 of the nation's 10.7 million unemployed workers were receiving weekly unemployment benefits under federal and state unemployment compensation programs, official compilations by the Labor Department show.

That means only 38.6 percent of the jobless are getting assistance from the nation's major program to help people when they lose their jobs and can't find another.

The figure has been dropping steadily in recent months for a variety of reasons, and the total receiving benefits would be 842,836 lower if Congress had not enacted an emergency program giving extra weeks to people who had exhausted their benefits under the programs.

The current proportion contrasts sharply with the figures for 1975, the height of the last major recession.

In February, March and April 1975, 65 to 69 percent of the total jobless were receiving unemployment compensation, double the current proportion.

Labor experts say there are several major reasons for the sharp contrast between 1975 and the current situation.

One is the protracted length of the current recession, which lasted nearly two years and came right after an earlier, less severe recession near the end of the Carter administration.

Under existing law, to get any benefits a person must work for a certain "base period" in the year before becoming jobless. Because the current recession lasted so long, many people have been out of work a long time and have used up all benefits and special extensions but have never gotten a new job that would enable them to establish a new "base period." So while they are still unemployed and swelling the overall jobless totals, they are not on unemployment insurance.

A second result of the great length of the current recession is that states with long-term, persistent high unemployment rates may fail to meet the unemployment growth "trigger" in the program formula for what is called "extended benefits."

At present there is a three-tier system of benefits: regular benefits (usually 26 weeks); an added 13 weeks of "extended benefits" in states that meet certain rates and in addition have unemployment 20 percent higher than at certain times over the previous two years; and up to 14 additional weeks of federally financed benefits in states that meet certain conditions.

Even though a state like Michigan still has 13.1 percent overall unemployment and Illinois 11.7 percent, both have dropped off the 13-week tier of benefits because they don't meet the 20 percent requirement. In fact, all states but Louisiana and West Virginia have dropped off the 13-week tier because unemployment, while still 9.5 percent nationally, has declined slightly in recent months and the states don't meet the 20 percent requirement.

Another reason for the low proportion of jobless receiving benefits is a series of program alterations that President Reagan pushed through Congress two years ago.

Reagan's changes, in effect, made it harder for states to qualify for the 13-week tier of extended benefits. If these changes had not been made, an added 485,000 people would be receiving benefits now, according to Labor Department calculations.

Although the figures show only 4.134 million unemployed people are receiving benefits while the other 6.6 million jobless are not, the impact may not be quite as great as the figures suggest because many jobless workers have a wife, husband or child working.

Overall, according to the latest figures, about half the total jobless have at least one person in their immediate family working full time.