President Reagan celebrated the 75th anniversary of the FBI yesterday by renewing his vow that the administration will "break the power of the mob in America, and nothing short of it."

Speaking at an outdoor ceremony attended by several thousand FBI employes at the J. Edgar Hoover Building, the president also called on the FBI to "detect and counter the increasingly hostile intelligence threat to our country" from Soviet spies attempting to steal American technology.

Reagan repeated a pledge he has made periodically over the last nine months to attack "the criminal networks and syndicates that have been tolerated in America for too long."

"On this, your 75th anniversary, I ask you to redouble your efforts to break apart and ultimately cripple the criminal syndicates in America," Reagan told the crowd gathered in the courtyard of the Hoover building.

The president made no reference to his proposal last Oct. 14 for a national commission to study the impact of organized crime in the United States. Members of the commission are expected to be named soon by the White House, with Judge Irving R. Kaufman of the U.S. Court of Appeals for the Second Circuit in New York as chairman.

Congress recently gave the administration permission to re-program $500,000 in fiscal 1983 funds to start the commission. For fiscal 1984, according to congressional officials, Reagan is expected to receive the full $2.5 million he requested for the commission.

Flanked by FBI Director William H. Webster and Attorney General William French Smith, the president yesterday was made an "honorary" special agent and was awarded an agent's badge, which he insisted on carrying off the stage himself in a wooden box tucked under his arm. The award previously has gone to Presidents Eisenhower, Kennedy, Johnson, Nixon and Ford, and several attorneys general, among others.

In an eight-minute speech, Reagan praised FBI agents as "a first line of defense against mobsters, spies, corrupt officials and other professional wrongdoers who prey on the innocent and undermine the moral foundations of our society."

Reagan said he wanted the FBI to "continue to give the highest priority to deterring and countering hostile intelligence activities in the United States." He also hailed the FBI role in his administration's campaign against drug smuggling.

The president made an indirect reference to the controversy that surrounded some of the FBI's activites in the 1960s and 1970s, calling that a "painful era in American history" when "our proudest values and most important institutions were called into question."

But, he added, "as mindless and destructive as some of the criticism was," those values and institutions became better understood.

In signing a proclamation designating yesterday as "FBI Day," Reagan, 72, joked, "It's nice to recognize something in Washington that's older than I am."