Suburban America's population surged by nearly a third in the 1970s while growth in the major cities continued to decline, according to an analysis of the 1980 census the Commerce Department is to release today.

The report also found that one third of the nation now lives in the five largest states--California, New York, Texas, Pennsylvania and Illinois--but its most striking news was the explosive suburban migration.

"The greatest growth we're seeing isn't in small-town America, it's in the small cities and suburbs surrounding the large urban centers," said Robert C. Speaker, chief of the Census Bureau's Population Distribution Branch. "The cores of these urban concentrations are either growing very slowly or losing population while while the small cities that ring them are growing very quickly."

Small cities and towns with populations between 10,000 and 50,000 grew 30.1 percent over the decade, while cities with more than 100,000 residents grew just 1.9 percent, the report said. More than two-thirds of the small cities and towns were associated with nearby large cities, Speaker added.

During the 1970s, the nation's total population grew 11.4 percent, to 226,504,825. The most recent population estimate "as of 8 o'clock yesterday morning," Speaker said, was 233,717,242.

Speaker said the growth in towns and small cities surrounding major cities continues a trend that began in the 1920s.

"Since the first census in 1790, the urban areas have grown faster than the rural areas," Speaker said. "But in the 1920s, with mass transit and the advent of the automobile, suburbanization started. Today, that's where most of the growth occurs."

Population patterns in the Washington metropolitan area reflect the national trends the latest report identified.

While the area's population grew 5 percent overall between 1970 and 1980, to 3.06 million, the center city actually lost residents during the period. Population in the District of Columbia slipped 16 percent during the decade, to 638,333, while the suburbs grew 12 percent.

Washington's modest population gains in the past decade contrast sharply with the 37 percent increase the area absorbed between the 1960 and 1970 censuses.

While population in most Washington suburbs surged, Arlington County posted a 12 percent decline between 1970 and 1980. During the same period, Charles County in Maryland and Loudoun County in Virginia expanded by more than half, while Prince William and Fairfax counties grew by about one-third.

Twenty-five of the nation's 3,137 counties had populations of 1 million or more in 1980, while 25 had fewer than 1,000 residents. The largest county was Los Angeles County with 7,477,503 residents, and the smallest was Loving County, Tex., population 91.