Prince George's County Council member Sue V. Mills said yesterday that she will introduce legislation to repeal a $1 million tax break for the Washington Capitals ice hockey team approved by the council in August.

Mills, who cast the lone dissenting vote when the measure was approved 10 to 1, said repeatedly during her successful reelection campaign that she would push legislation to overturn the tax break. Mills contended yesterday that changes in the council membership as a result of the Nov. 2 election have given her the votes needed to overturn the measure.

Mills said she will introduce legislation to revoke the tax break "as soon as I can," which could be as early as the first meeting of the new council on Dec. 7.

Abe Pollin, owner of the Capitals, threatened earlier this year to move the hockey team out of its home at the Capital Centre in Largo unless four conditions were met, one of which was approval of the tax reduction. Pollin said the team was losing $3 million a year.

Since that vote was taken, a new nine-member council has been elected, reduced by two members as a result of redistricting. Mills said yesterday that she had the support of four newly elected members, which, along with her vote, would make up a five-member majority.

The success of Mills' effort is in doubt. She declined to name the other four whose support she anticipates, saying she had not talked to them since around the general election. Newly elected council member James Herl said last night he would support repeal of the tax break; new member Hilda Pemberton said she would not. Another new member, Richard Castaldi, said he would not support repeal at this time. Two others, JoAnn Bell and Anthony Cicoria, could not be reached for comment.

Only three of the 10 members who voted for the tax break, William Amonett, Frank Casula and Floyd Wilson, are returning to the County Council.

Mills said yesterday that the council had voted to "support a failing business. The Caps are still losing. That's part of the problem Pollin has. People are not going to the games because they don't have anything to see."

The legislation approved by the council reduces the county amusement tax on the Capitals from 10 percent to 1/2 of 1 percent during the next two years. After that, the tax gradually would climb back up until it reaches 10 percent again in 1988.