The Senate Ethics Committee ordered fulltime federal protection yesterday for the chief witness in the case against Sen. Herman E. Talmadge (D-Ga.).

The action came after committee officials received two anonymous telephone calls Tuesday warning that Daniel Minchew's 2-year-old daughter will be killed if he testifies.

Chairman Adlai E. Stevenson (D-Ill.) said the committee ordered U.S. marshals to watch Minchew's Chevy Chase home and protect his family. Stevenson declined to elaborate but other knowledgeable sources said the death threats were voiced by a male to Stevenson's office and to the private law office of committee special counsel Carl Eardley.

Minchew's attorney, Robert Fierer, said yesterday that his client would testify as planned. Minchew will probably appear before the ethics panel early next week in a Senate hearing room with beefed up security.

Talmadge's office issued a statement deploring the death threats. "It is unconscionable to think that any rational person would make such a threat against an innocent child," the Georgia Democrat said. "I hope that the person responsible will be discovered and punished . . . and that the Minchew family will be afforded every possible protection."

Minchew's testimony is expected to be the keystone in the case against Talmadge. So far the six-member ethics panel has heard nearly three weeks of testimony mostly from expert witnesses and Talmadge staff members loyal to the senator.

Talmadge is facing five charges of financial misconduct. The most serious charges - that he knew of improper Senate reimbursements to his office and converted campaign funds to his own use - are linked to information supplied by Minchew.

Minchew has testified in executive session to the committee that he set up and ran a secret bank account for Talmadge here with the senator's knowledge. According to Minchew, who was Talmadge's chief aide until 1974, bothe he and the senator got some of the $39,000 in improper Senate reimbursements and mostly unreported campaign contributions that went into the secret bank account.

Talmadge has denied any knowledge of the account and called Minchew "a proven liar cheat and embezzler."

In testimony yesterday, Lawrence W. Earls, Talmadge's accountant since 1972, told the ethics panel that Talmadge had instructed him "to do what was right" in handling the senator's finances.

Earls, a tax partner in the national accounting firm of Peat, Marwick, Mitchell and Co., told the committee that he handled a ticklish dispute between Talmadge and his former wife, Betty, over a $755,000 land sale in 1972 by leaving the money off Talmadge's Senate financial disclosures for five years.

Although Talmadge bought the land himself with a group of Georgia investors, he placed his share in his wife's name. When the land was sold she paid the capital gains taxes on their profit.

One of the charges against Talmadge is that he incorrectly reported taxes on gifts to his wife. Talmadge has called the charge "minor" and said at most its was "a good-faith failure to report at a time when the legal situation was not clear." CAPTION: Picture, DANIEL MINCHEW . . . to testify as planned