WASHINGTON (AP) _ Raymond J. O'Connor, citing personal and family reasons, resigned abruptly today as chairman of the Federal Energy Regulatory Commission that regulates the natural gas, electric utility and oil pipeline industries.

A former New York investment banker before assuming the $73,000-a-year job as the commission's chairman in November 1983, O'Connor notified the White House this morning that he wanted to resign effective Jan. 31.

''Personal and family reasons made it necessary to resign at this time and return to New York City where we have made our home for many years,'' O'Connor said in a written statement on his decision.

Rachelle Patterson, a spokeswoman for the agency, said no other reason for the resignation was given.

O'Connor, 53, had said in interviews last year that he intended to stay in the job until his term on the five-member commission expired in October 1987.

But his activism in restructuring the natural gas industry to induce more competition while still maintaining the federal prices ceilings ordered by Congress on some categories of gas had angered pipelines, producers and officials in the Reagan administration.

Under his leadership, FERC last year proposed, but then retreated on issuing a set of new regulations to preserve cheap, so-called ''old'' supplies of gas for primarily residential and small business users.

The new regulations effectively would have transferred about $5 billion a year in producer revenues to consumer savings on natural gas.

According to energy and political analysts, that change, if adopted, would have ended any chance for totally decontrolling natural gas prices, which has been the administration's chief legislative priority on energy for five years.

As a counterattack to the FERC move, Energy Secretary John Herrington called upon a little-noticed and never-before-used provision in energy laws to formally demand that the commission instead consider deregulating natural gas prices administratively. Hearings on Herrington's proposal are scheduled later this year.

The White House also named two new commissioners to the agency in November. One of them, Charles Trabandt, a former Senate Energy Committee expert, has played an activist role the past two months in seeking speedy action on Herrington's proposal.

O'Connor, a former executive vice president at Prudential-Bache Securities Inc., also had launched a similar initiative to bring more competition into the electric utility industry and end some of its monopoly protections.

While at Prudential-Bache, O'Connor had handled the financing of several atomic power plants for some of the nation's largest nuclear utilities, including Commonwealth Edison in Illinois and Pennsylvania Power & Light Co.