In an unprecedented action, the National Park Service has refused to let militant Iranian students, who sparked bloody fighting here Nov. 15 during the visit of the shah of Iran, hold another protest rally near the White House Thursday.

Citing a "clear and present danger to public safety," park service regional director Manus (Jack) Fish issued the denial of the demonstration permit early yesterday afternoon.

Student organizers say they may seek a court injunction today to reverse the denial.

Park service officials said they could not recall denying nay political demonstration permits in the past, even during the volatile antiway days of the late 1960s, on the basis of "clear and present danger" to public safety.

The officials said, however, that the Nov. 15 demonstration was especially violent - 124 demonstrators and police were injured in hand-to-hand fighting - and there had been an insufficient "cooling off" period since then.

Hundreds of masked, stick-wielding anti-shah students on Nov. 15 attacked pro-shah demonstrators on the Ellipse during the ceremonial arrival of Shah Mohammad Reza Pahlavi at the White House.

A small detail of U.S. Park Police on the Ellipse was caught by surprise and overwhelmed until reinforcements arrived and the students were routed with tear gas.

The incident triggered criticism by some rank-and-file park police officers who said their supervisors had failed to prepare for the onslaught. Park plice also apparently discounted advance warnings of possible trouble given them by both the FBI and State Department security officials.

Student organizers have denied initiating the attack, blaming it on provocateurs of SAVAK, the Iranian secret police.

While the park service has denied the students' demonstration permit for Lafayette Park or the White House sidewald, D.C. Police have tentatively approved a permit for the students to march on the Iranian embassy on Thursday.

Asked why the same "clear and present danger" principle would not apply to the march permit as the demonstration permit, Capt. Joe Mazur of the D.C. Police special operations division said:

"When they've marched to the embassy before, we never had any trouble with them . . . The danger is when you have a rally like in Lafayette Park with speakers and sound system. It entices them."

The parade permit povides for 200 demonstrators to march on sidewalks from Vermont Avenue and N Street NW to Massachusetts Avenue and Waterside Drive NW near the Iranian embassy at 3005 Massachusetts Ave. NW.

Organizers say they want to protest the recent crackdown on political dissidents in Iran and to protest the upcoming visit of President Carter to that country.

The denial of the demonstration permit by park service regional director Fish was based on a provision of the Code of Federal Regulations authorizing a denial which it "reasonablyappears" that there is a "clear and present danger to public safety and good order."

Fish "agonized over this quite a bit" in an attempt to balance First Amendment rights with public safety, said one official. "He was reluctant to deny the permit."

Amendment rights with public safety, said one official. "He was reluctant to deny the permit."

Fish's formal letter of denial to the Iranian Student Association in the United States noted, however, that the students's previous demonstration occurred a "mere three weeks ago" and resulted in "vicious attacks on other demonstrators, bystanders and police."

He said both the Park Police and Secret Service had urged him to deny the permit, and "also, I took into consideration that the activities you proposed for (Thursday) are in the same area and of the same character as those which you proposed on Nov. 15."

The Iranian Student Association in the United States is one of several Iranian student factions and is noted according to park service officials for its militancy. WHile its only formal organizational position is one of general opposition to the shah's regime, its members comprise a wide cross-section of Marxists, Maoists, non-communist socialists and others, many of whom support the two principal armed resistance movements in Iran, the Organization of Peoples Majahedin and the Organization of Fadian of Iran.