It is no wonder that President Reagan tried two years ago to keep Paula Stern from becoming the chairman of the International Trade Commission. The once-sleepy little agency has emerged as the place more American businesses are going to seek relief from foreign competition.

Since taking over as head of the independent, quasijudicial agency 16 months ago, Stern has become more outspoken over what she sees as the Reagan administration's failure to deal with record trade deficits and the havoc they are causing the U.S. economy.

"In international trade," she told the National Electrical Manufacturers Association last month, "we are operating with neither a battle plan nor a general staff. No wonder we are in full, disorderly retreat."

"Because the federal government doesn't make trade a priority," she said in a speech to the American Stock Exchange International Investors Conference last week, "we don't make headway against the competition."

What's next? Stay tuned. On Thursday, Stern, a Democrat whom President Carter appointed to the ITC seven years ago last week, addresses the National Press Club.

A thoughtful specialist in international affairs, Stern consistently has pointed to the damage Reaganomics was doing to American industries. She blamed a surge of imports more on the supercharged dollar than on unfair trade practices by foreign competitors.

But she does not share the view of many Democrats that unfair practices by foreign competitors are the major cause of America's trade woes. Calling unfair trade "an irritant, not a life-threatening assault," Stern calculated that less than 5 percent of last year's $350 billion in imports would have been challenged if all the charges brought before the ITC last year had been sustained.

"Too much of our attention focuses on a single aspect of trade -- the unfair practices of others," she said last week.

In an interview in her office decorated with drawings by her two children (one born since she was named to the ITC), Stern cited Reagan's decision to overrule commission recommendations that quotas be placed on footwear imports as "a perfect example of a lack of leadership in trade, the lack of a trade strategy."

"Had there been some recognition that we had a trade problem and that the strong dollar is not a sign of strength but the reason for the trade deficit, there would have been a willingness to deal with the problem," she said.

Stern said the ITC had "extremely limited" remedies to offer the shoe companies and workers, especially since the Reagan administration, in effect, had ruled out adjustment assistance for dying industries and their employes.

But she said she is not angry that Reagan rejected the ITC recommendation since the president has to consider a range of issues, including the ramifications and the total economic costs of his decision, while the commission examines only the economy of the industry.

What upsets Stern most is that trade plays such a minor role in formulating economic policy. "American policy makers have to accord trade issues priority status instead of a stepchild's role in the formulation of fiscal and monetary policy," she said. "They would have to consider the pending tax reform proposals, for example, in terms of their impact on different investment sectors and on future competitive strength."

In her American Stock Exchange speech, Stern made a proposal sure to be an anathema in the magic-of-the-marketplace atmosphere of the White House: a cooperative effort by business, labor and government that smacks of the 1983 Democratic idea of industrial policy. But Stern never uses the words "industrial policy," which have the taint of "planned economy." Instead, she talks about increasing competition.

"On a national scale," she said, "such cooperative efforts must begin with the realization that decisions on investment, taxation, regulation and even education determine our ability to compete."

"In those fields, the federal government now makes its choices with little or no attention to their impact on our trade balance. . . . Government, however, has the opportunity to begin a bargaining process with business and with labor on new ways to maximize American strength."