In the second major breakthrough in The Washington Star's intensive labor negotiations, the Washington-Baltimore Newspaper Guild reached tentative agreement yesterday with the newspaper on a new five-year contract.

The guild-which represents about 475 news, editorial, advertising, clerical and other white-collar employes-announced the tentative accord five days before the newspaper's Dec. 31 bargaining deadline.Time Inc., which bought The Star earlier this year, has threatened to close it on New Year's Day unless all 11 unions representing Star employes have accepted new contracts before then.

The guild has scheduled a meeting of Star employes Friday to ratify or reject the tentative agreement. Last week, delivery truck drivers and othe circulation employes represented by Local 639 of the International Brotherhood of Teamsters ratified a contract.

According to guild negotiator Raymond G. Dick, the guild persuaded The Stars's management to abandon its initial demand for a five-year freeze in basic wage schedules for white-collar employes. Dick said management also dropped a proposed provision that would have allowd The Star to deny any salary increase during the next five years to 10 percent of the newspaper's highest-paid employes.

Dick said management won several significant concessions from guild negotiators, including relatively small guaranteed wage increases for high- salaried employes, a new clause outlining various unspecified "management rights" to which the Guild had objected and for the first time a contractual no-strike provision.

Under complex terms of the proposed agreement, as outlined by Dick, guild employes at The Star would be divided into two broad salary groupings-those earnings $471.12 a week or more and those who earn less.

Employes who earn at least $471.12 a week-about $24,500 a year-would be guaranteed a weekly wage rise of $28.88 Jan. 1 and an additional $14.40 on Jan. 1, 1980. There would be no basic salary increase for these employes in 1981. Increases in 1982 and 1983, Dick said, would be determined through a wage reopener provision and would be subject to binding arbitration.

In addition to these basic pay increases, Dick said, the 191 Guild employes currently earning at least $471.12 a week would be eligible for merit increases, drawn from a new "merit pool" that would amount to about $675,000 during the first three years of the contract. Management would have broad latitude in providing such merit raises. In addition, 33 advertising salesmen would be eligible for other incentive bonuses.

The second overall salary grouping would include Guild employees who earn less than $471.12 a week. These workers, Dick said, would receive salary increases, ranging from $22 to $31 a week on Jan. 1, additional weekly raises varying from $21 to $30 the next year, and weekly wage rises of $22 to $31 on Jan. 1, 1981. A wage reopener provision would apply in 1982 and 1983.

Union officials previously said that The Star's management had proposed to freeze the key contractual minimum salary of fully experienced news and other employes at about $490 week throughout all five years of a new contract. Under the tentative agreement yesterday, Dick said, the key minimum would rise to $500 Jan. 1 and to $514.40 on Jan. 1, 1980. It would be renegotiated in 1982 and 1983, he said.

Dick said the proposed contract is "the best we can get" although he said it still has significant drawbacks. He said the guild's negotiating team would not offer any "blanket recommendation" to the members at Friday's meeting.

A Star representative quoted Star publisher Georg W. Hoyt yesterday as saying he was "extremely pleased that we've come to agreement with the Guild. However, it still has to be ratified by the members."

The Teamsters pact ratified last week would apply to nearly 300 employes at The Star. Two other Teamsters contracts, affecting 150 to 200 employes, are still under negotiation.

The Washington-Baltimore Newspaper Guild and Teamsters Lical 639 are the two largest unions representing Star employes. Among other major contracts under negotiation are those involving printers, pressmen and mailers.

In one further development yesterday, Columbia Typographical Union No. 101, which represents about 175, Star printers, held its second bargaining season with The Star's management since Friday, according to union officials.

Talks between The Star and the typographical union had halted for 10 days, union officials said, because of sharp disagreements over the Star's plan to eliminate 80 printing jobs by June and to reduce its printing staff to as few as 25 employes during the next five years.

According to Star officials and some union leaders, two other small unions have also reached tentative contract agreements with the newspaper. These have been identified as Service Employees International Union 82, which represents about 20 maintenance workers at The Star, and Local 26 of the International Brotherhood of Electrical Workers, which represents a small number of electricians.

Officials of the two unions have declined, however, to confirm that tentative agreements have been completed.