After a year of rapidly rising profits, Giant Food Inc. yesterday declared a three-for-one stock split and boosted its cash dividend by 38 percent.

As a result of the split and dividend increase, a stockholder who now owns 100 shares of Giant paying annual dividends of $130 will hold 300 shares paying total dividends of $180 a year.

The new quarterly dividend will be 15 cents a share, the equivalent of 45 cents before the split. The quarterly dividend previously was 32.5 cents a share.

Both the stock split and the increased dividend will be paid March 11 to those who are shareholders as of Jan. 31.

Trading in Giant stock, which was halted Tuesday pending the company's announcement of the stock split, is expected to resume today. The shares last sold at 56 5/8.

Giant's profits were up 13 percent in the third quarter to a record $7.6 million ($1.57 a share) from $6.8 million ($1.38). Profits for the first nine months of its fiscal year totaled $24.1 million ($4.91) compared with $4.5 million (92 cents) a year ago when it was suffering from a food-price war.

Sales at Giant's 130 supermarkets were up 10 percent to $1.25 billion for the nine months ended Nov. 6 and the chain's profits as a percent of sales climbed to a record 1.81 percent.

Yesterday's announcement followed the voting of shareholders to increase the number of Class A nonvoting shares from 8,136,000 to 20 million. The split will bring to 14,373,000 the number of Class A shares outstanding.

The Cohen and Lehrman families who founded the chain hold 250,000 voting shares.