For eight years, Sarah Jackson says, her food stamp routine was always the same. Each month she would plunk down $106 and get back $260 worth of food stamps.

Jackson, a resident of the 1000 block of 5th St. NE, said she used the stamps to feed herself and her five grandchildren.

But in January the food stamp rules changed, and with the changes went Jackson's certainty of knowing the amount of food stamps she would receive each month.

Under a new food stamp system, Jackson began to receive $168 in food stamps free of charge each month. Just as she was adjusting to this new system, Jackson learned that her benefits would change again in June when she will receive $143 in food stamps.

However, under still newer guidelines, Jackson's benefits will change for the third time in July when she receives $162 worth of food stamps.

What has happened is that new guidelines for July will replace the March guidelines which, in turn, replaced the January guidelines.

"I wish they would put them (food stamps) back like they were before, even if I have to pay," Jackson said.

Jackson, who supports her family on $577 a month from disability, welfare and Social Security benefits, said she found the old system to be dependable - even though she had to pay for food stamps.

The way the food stamp program is set up now, changing frequently, she said, "My children are going to go hungry."

Jackson's situation is shared by about 37,000 District families (or about 90,000 persons) who have been reeling under the yo-yo syndrome of the new food stamp system, city officials said.

Under the current system, food stamp benefits are adjusted twice a year - once on Jan. 1 and once on July 1 - based on increases in the cost of living. Income eligibility limits are set annually on July 1. However, income limits were also set in March of this year as the result of the revised Food Stamp Act of 1977.

Under that revision, all 50 states are required to review food stamp applications by June 30 using the March income eligibility guidelines.

Recently, these income eligibility reviews were completed for 34,997 District families (representing about 84,000 persons). Beginning in June, 27,498 families (representing about 65,995 persons) will receive a modest increase in monthly food stamp benefits. The average increase will be about $7.65 worth of food stamps.

However, some 5,445 families (representing about 13,068 persons) will have their food stamp benefits reduced by about $10.56, and 1,159 families (representing about 2,781 persons) will lose their food stamp benefits altogether. The food stamp benefits of 895 families (representing about 2,148 persons) wil remain the same.

But those figures will change again in July when the new eligibility guidelines go into effect.

"Some of these people we have dropped will be eligible again as of July 1," said William Gray, acting chief of the food stamp eligibility office, the Department of Human Resources.

DHR director Albert P. Russo said letters will be sent to the 1,159 families who have lost food stamp benefits, urging them to reapply in June. They were notified of their termination from the program May 16, Russo said.

Other recent federal changes in the program include: increases in food stamp benefits, and changes in the maximum net incomes and standard deductions allowed to help a family become eligible to receive the stamps.

For examplee, before January, Sarah Jackson was allowed multiple deductions, including child care and medical costs, with the proviso that her monthly net income could not exceed $867 after deductions.

In January, when the program began to change, the maximum net monthly income for a family of six rose to $913. In March, it dropped to $719 and in July it will rise to $790.

In March, restrictions were also placed on the income deductions allowed. Deductions now allowed are: a $65 standard deduction, a deduction of up to $80 for child care and/or shelter costs and a 20 percent deduction of earned income.

In July, however, the $65 standard deduction will be raised to $70 and the deduction for child care and/or shelter deductions will be raised to $90.

"They're very complicated," Gary said of the food stamp regulations which the federal government changed in an effort to simplify the program. "It's going to be difficult to implement the whole thing. Yet the advantages (to food stamp recipients) outweigh the disadvantages."

Heading the advantages, Gray said, are changes that now make the stamps free and that allow food stamp applicants without access to cooking facilities to qualify for the program.

Despite these advantages, there are further complications to the program.

At present, the U.S. Department of Agriculture is asking Congress for $650 million in emergency monies to keep the nearly depleted fund for the food stamp program going until Oct. 1, when the 1980 fiscal year begins, said Leslie Wilder, information officer for the USDA regional office in Washington.

If the emergency funds are not received by July, all 19.1 million people now receiving food stamps will have their benefits cut by one-third. If the money is denied until August, food stamp benefits will be cut in half. If the funds do not come by September, "no one will get anything in Septemer," Wilder said.

The emergency funds were requested, Wilder said, because federal officials underestimated the increases in food costs and people's urgency to apply for the program. In figuring the $6.2 billion budget needed to administer the program, Wilder said, experts estimated that food costs would not rise by more than 3 percent a year.

Instead, food costs "went up 22 percent in the past two years and people came into the food stamp program faster than expected," she said.

An additional $700 million in supplemental funds will be needed to run the program in 1980, she said.