President Reagan appealed to high-technology workers today to support his tax plan by attacking lobbyists, special interests, bureaucrats and "so-called experts and Washington sophisticates" that he said seek to stop it.

In the second day of campaigning outside Washington for his tax-overhaul plan, Reagan spoke scornfully of the capital and sought to build resentment against those seeking to stall his proposal.

"Right now, the army of lobbyists and special interests are dug in around the Capitol building, firing every weapon in their arsenal in an attempt to shoot down our proposal for tax fairness and simplification," he told several thousand workers outside the Great Valley Corporate Center.

"They're allied with the Washington sophisticates and so-called experts who tell us that tax-simplification will never pass, that it challenges too many of those interests and takes away the special privileges of a powerful few who like the present tax code just fine," he said.

"But I think the sophisticates and the lobbyists and the experts have forgotten one thing. They've forgotten about you," he added. "They've forgotten about the rest of America that exists beyond the shores of the Potomac."

Reagan also persisted in explaining his proposal as a tax cut. "It will mean tax relief for American families, individuals and businesses . . . . It will not be a tax increase," he said.

In fact, the Reagan plan, by his estimates, would mean a 22.5 percent increase in corporate-tax payments and a 5.2 percent reduction in individual payments by 1990. It would produce a tax cut for 58.1 percent of American families, no change for 21.2 percent and a tax increase for 20.7 percent.

Seeking to demonstrate support for his plan, Reagan questioned his listeners:

"Do the people of Pennsylvania want a tax system that's needlessly complicated and unfair?"

"No!" they shouted.

"I can hear you," Reagan said, "but the walls of that Capitol building are pretty thick."

The crowd seemed somewhat less enthusiastic when Reagan asked, "Do you want a tax system of, by and for the tax lawyers?" There were shouts of "no," but many people were silent.

The White House intended to use the industry center here to underscore advantages in Reagan's plan for such emerging high-technology companies, including lower capital-gains tax rates.

"I've heard that some of the advanced technologies up here are working on what they call 'very large integrated systems,' " Reagan said. "Now that's nothing new to me. Most of the time in Washington I feel like I'm working with a very large disintegrating system."

"Maybe even, someday, high-tech will invent a cure for the bureaucracy down in Washington," he said to laughter.

"I have to confess, I'm not very up to date on all this new high-tech computer lingo," he said. "I thought hacking meant what the Congress was trying to do lately to the defense budget."

At a luncheon today, R. James Macaleer of SMS Inc., whose firm provides time-sharing computer systems for hospitals, was seen motioning to Reagan and heard objecting to a provision relating to employe stock options. White House aides ushered reporters out of the room.

Since announcing his plan Tuesday, Reagan has given five speeches about it but answered no questions from reporters about the decisions he made.

Reagan said today that his tax plan would "ignite the second stage of our booster rocket and blast this economy to new heights of achievement."