Small businesses in Arlington County would be the main beneficiaries of $1.2 million in tax cuts under a proposal to be considered next month by the Arlington County Board.

"The County Board will definitely roll back the business license taxes by $1.2 million," said board Chairman Stephen H. Detwiler. "The question with the $1.2 million this year is who gets in front of the line. The small businesses deserve to be at the front of the line."

The proposed cuts, required under state law, have the support of many county officials and members of the business community, who hope the reductions will aid businesses suffering from recent economic setbacks.

". . . Concentrating 1983 reductions on small businesses, local merchants, and 'mobile' professions . . . could provide stimulus for the Arlington economy," according to a report by the Fiscal Affairs Advisory Committee, a citizens' panel appointed by the County Board to draw up a package outlining the proposed cuts.

"We're pleased that the bulk of the impact will be directed toward the small-business community in Arlington," said David M. Guernsey, a vice president of the Arlington Chamber of Commerce who is chairman of the chamber's small-business council. "Considering the turbulent economic times that small businesses are facing . . . this is definitely a benefit to them."

State law requires local jurisdictions that exceed certain state ceilings for business tax rates to reduce some rates beginning next year. Under a state formula that considers a jurisdiction's current rates plus overall revenues from business taxes, Arlington must reduce its business tax revenues by an estimated $1.2 million in 1983. If business tax revenues continue above state ceilings, more reductions would be required, and County Board members say it is likely Arlington will have to make further cuts.

Alexandria officials say they expect to make some reductions. Fairfax officials could not be reached for comment.

In Arlington, County Board members hope to make small businesses a priority for receiving reductions.

". . . Small businesses should be a first area of concern," said board member Ellen Bozman.

Arlington officials also hope to make the county's business tax rates more competitive with its neighbors.

"Arlington rates tend to be much higher than surrounding jurisdictions," said Naomi C. Klaus, deputy Arlington revenue commissioner.

One result of the reductions, some county officials hope, will be to improve the Arlington business climate.

"We hope that it cuts will encourage businesses to stay or relocate in Arlington," especially if businesses are aware of the prospects of future cuts, said fiscal affairs committee member Loretta J. Shogren, who worked on the proposed reductions after meeting with county staff and local business groups.

The fiscal affairs committee has proposed changes in several categories, and a major change for some business occupations would be switching from flat rates, such as $25 a year, to rates based on each $100 of gross receipts.

Among the committee's recommendations:

* Professional occupations. The rate for professionals, such as lawyers, doctors, and consultants, would be 87 cents for each $100 of gross receipts. The current Arlington rate is $1 per $100 of gross receipts. In Alexandria, the rate is 60 cents per $100, and in Fairfax, 31 cents per $100.

* Restaurants. The rate would be reduced to 70 cents for each $100 of gross receipts, compared with the current rate of 90 cents per $100. Restaurants pay 35 cents per $100 in Alexandria and 17 cents per $100 in Fairfax.

* General retail merchants. The rate would be reduced to 26 cents for each $100 of gross receipts, down from the current rate of 29 cents per $100. General retail merchants pay 35 cents per $100 in Alexandria and 17 cents per $100 in Fairfax.

* Real estate brokers and salesmen. The new rate would be 95 cents per $100, down from $1 per $100. Real estate brokers pay 60 cents per $100 in Alexandria and 31 cents per $100 in Fairfax.