A key aide to Sen. Herman E. Talmadge (D-Ga.) yesterday called the senator's chief accuser in his financial misconduct case a devious and indirect man who misused his post in another federal agency after he left Talmadge.

Allyne Tisdale, a soft-spoken financial secretary to Talmadge, also lashed out at the senator's former wife, Betty, saying that she threw a three-day temper tantrum in Talmadge's office in 1974.

Betty Talmadge, who divorced the senator in 1977, is expected to provide damaging information on Talmadge's private cash flow when she testifies before the Senate Select Committee on Ethics in about two weeks.

The committee, which ended its firstweek of hearings on the Talmadge case yesterday, is looking into five allegations of financial wrongdoing against Talmadge.

In her third day of testimony yesterday, Tisdale, who has worked for Talmadge since 1966, told the ethics panel that Betty Talmadge was irrational when she stormed into the senator's office here on Jan. 21, 1974, and began berating Talmadge's chief aide, Daniel Minchew.

"Mrs. Talmadge didn't seem like Mrs. Talmadge," Tisdale said.

"She said she had put Sen. Talmadge where he was and everybody, including Sen. Talmadge, was going to work for her in the future."

Talmadge and his wife were in the midst of a bitter breakup at the time. They were divorced in 1977.

According to Tisdale, Betty Talmadge wrote herself a $21,100 check during the 1974 incident in the senator's office, although payment was later stopped on the check by the senator. Tisdale said Mrs. Talmadge fired Minchew and then "took up her post" at Minchew's desk for three days, rifling his office records.

Tisdale said Mrs. Talmadge also threw a wood carving at Minchew. Minchew left the office for several days, she said, but returned later to his duties. Tisdale offered no explanation of what prompted the incident.

Last month Talmadge's former wife gave the Ethics Committee 77 $100 bills she said were part of a secret cache kept by Talmadge in an over-coat in their apartment in Washington until 1974. Talmadge is accused of overseeing the diversion of funds from Senate office reimbursements and campaign contributions into his own bank account.

In her testimony yesterday, Tisdale attacked the credibility of Minchew, who is the chief Ethics Committee witness against Talmadge.

She said she worked for Minchew in 1975 and early 1976 at the International Trade Commission. But she left, she said, and returned to Talmadge's office because Minchew spent too much working time on personal matters and used his staff to run errands. She said Minchew also had trouble getting along with commission officials.

At the trade commission, Tisdale said, she once had to spend a Saturday night tracking down building contractors working on a townhouse Minchew was having renovated on Capitol Hill. On another occasion, she said, a trade commission vehicle was used to pick up chandeliers for the town-house.

Tisdale also portrayed Minchew as actively involved in real estate transactions during 1975, after he left Talmadge's office. During that year, she said, he purchased the Capitol Hill townhouse and two suburban farms.

Talmadge's attorneys have claimed Minchew was deeply in debt during 1974, when money was diverted by Minchew through a secret bank account from Talmadge's office funds. Talmadge has called Minchew an "embezzler." CAPTION:

Picture, Sen. Herman E. Talmadge (D.Ga), flanked by his attorneys, James Hamilton and Ron Wortheim, confers during a session of the Senate Ethics Committee. AP