Giant Food, Inc., one of the two major food retailers in metropolitan Washinton, yesterday reported a slight decline in profits for both the fianl quarter and fiscal year ended Feb. 26.

Avemco Corp., in a separate earnings statement, reported record profits and insurance premium volume for the first qaurter of 1977.

Joseph B. Danzansky, president of the 112-supermarket Giant chain noted yesterday that the prior fiscal periods each included an extra week and that "when this fact is taken into account. Giant's earnings . . . have remained relatively stale."

For the 52-week-fiscal period ended Feb. 26. Giant's profits declined to $10.6 million ($3.21 a share) compared with $11.3 million ($3.38) in the 53-week, year-earlier period. Sales rose to $395 million from $833 million.

In the fourth quarter of the year, Giant earned $4 million ($1.19) in 16 weeks vs. $4.4 million ($1.31) in 17 weeks a year ago as sales increased to $292 million from $284 million.

Danzansky said the extra week in the prior year had "contributed disproportionately to earnings" for the year-earlier periods. At the same time, he said profits as a percentage of sales declined to 1.19 per cent in the recent year from 1.35 per cent a year earlier.

Avemco Corp., a Bethesda-based firm that offers insurance and financial services to the general aviation industry, said first-quarter profits were estimated at $500.000 (18 cents a share) compared with $329,494 (11 cents) a year earlier, when there were 100.000 more shares outstanding.

Chairman Arnold H. Johhson said gross insurance premiums written totaled a record $4.1 million in the quarter, up 19 per cent from the same period last year.