ATLANTA (AP) _ Southern Democrats chose their representatives to the national party's new Fairness Commission Saturday amid complaints that the selection process itself was unfair.

Members of the Southern caucus, which includes party chairmen, vice chairmen and National Committee members, also said the presidential nominating process is too long.

The party leaders selected 10 members of the new commission, created by the 1984 Democratic National Convention to review the fairness of the party's presidential nominating rules.

The group was presented with a slate of candidates by Southern caucus chairman Alan Diamonstein, who said it was the product of discussions with a variety of party activists. The slate was overwhelmingly approved, but not before a few Democrats charged the commission was being unfairly formed.

Irving Kaler, a Democratic National Committee member from Georgia, said he resented being excluded from the slatemaking process.

''I think it would have been fairer had you solicited all of our opinions on the construction of this slate,'' said Kaler, who campaigned unsuccessfully for a seat on the new commission.

The slate, approved by a vote of 59-12, include five men and five women, including three blacks, and representatives of all the Southern states except West Virginia, Alabama and South Carolina. State Democratic Party Chairman Bert Lance is the member from Georgia.

Two of the three black members selected were supporters of the Rev. Jesse Jackson's presidential candidacy - New Orleans Mayor Dutch Morial and Hinds County, Miss., Supervisor Bennie Thompson.

The Fairness Commission will have 50 members, including 10 chosen by each of the party's four regional caucuses and 10 appointed by Democratic National Committee Chairman Paul Kirk.

The party agreed to create the commission at last year's convention, as part of a compromise between Walter Mondale, the party's eventual nominee, and supporters of the unsuccessful candidacies of Jackson and Sen. Gary Hart (D- Colo.). Jackson and Hart had complained that the delegate selection rules had unfairly hindered their campaigns.

The group also discussed a regional primary. Presently, Georgia, Alabama and Florida hold their primaries on the second Tuesday in March. A measure is now pending in the Texas Legislature that would move that state's primary to the same day.