A General Accounting Office report released yesterday concluded that computerized trading equipment and the regulation of transactions should be overhauled to avoid another stock market plunge such as the one that occurred last October.

The GAO's study said the nation's various financial markets increasingly have come to affect one another, and that trading officials must find ways to prevent plummeting prices in one exchange from spilling into others.

But the GAO, an investigating agency for Congress, said government regulators also must keep up with the times as trading volumes grow and links become stronger among securities and futures markets at home and overseas.

"The history of the last 60 years makes clear the pivotal role in our economy which is played by the financial markets," Charles A. Bowsher, head of GAO, told the House telecommunications and finance subcommittee.

"The federal government cannot escape responsibility for assuring that such a vital mechanism performs effectively in the public interest," Bowsher added.

The preliminary study, on which research will continue, is the second major federal analysis of Wall Street's unprecedented October collapse. In the first 19 days of that month, the Dow Jones industrial average lost about one-third of its total value, or about $1 trillion. On Oct. 19 the Dow dropped 508 points, a 23 percent plunge.

A report Jan. 8 by a commission appointed by President Reagan and headed by investment banker Nicholas F. Brady recommended that the Federal Reserve or some other federal agency be given broader powers to oversee the markets, trading rules be tightened and limits be placed on price swings.

The GAO agreed that the government should do a better job of overseeing the markets, but stopped short of urging that the Fed get that job, stating only that "we believe that the Fed must be involved in some way with these markets."

The Fed did a good job of managing the money supply during October, Bowsher said, helping lessen the impact falling stock prices had elsewhere in the economy. But he said that a move by Congress to loosen laws regulating commercial banks' investments would make the Fed's job "significantly more complex and difficult."

The report noted that the New York Stock Exchange uses 12 computer systems, designed to handle transactions of 400 million shares daily at an average speed of two minutes per transaction.

But when volume peaked in mid-October, reaching 600 million shares daily Oct. 19 and 20, transactions took 10 to 75 minutes to complete, it said. Because of the volume, the report noted, nine computer systems had problems.

"Some orders were delayed or did not reach the trading floor for execution," the study said. "The automated systems problems affected not only the timely and efficient trading of stock at the {New York Stock} Exchange, but also affected the ability of other financial markets to trade securities" and other financial instruments.

Rep. Edward J. Markey (D-Mass.), chairman of the subcommittee, said, "In my view more deregulation is not the answer. Smart, modern and realistic regulation is."