The administration is finally getting ready to tackle one of the most complicated and heavily criticized set of regulations now on the books: the federal pension rules issued under the 1974 Employe Retirement Income Security Act (ERISA).

Large and small businesses have long complained that these rules are so onerous and costly that they have become counterproductive. For although they were issued to protect workers and guarantee them the pension benefits they are due, many companies--especially small ones --say the rules have lead them to abandon their pension programs rather than comply with ERISA rules.

Despite these complaints, Reagan's regulatory officials up to now have devoted relatively little attention to these rules. Although they have designated 100 regulations for review and possible relaxation, ERISA rules were not included in the three earlier hit lists issued by the administration as part of its regulatory-reform drive.

The reason, according to one ERISA expert, is that the law and its accompanying regulations are so complicated that few people understand them and their impact.

But government officials say the administration is now ready to devote serious attention to ERISA rules, probably making them the centerpiece of the administration's next hit list, expected sometime next month.

"ERISA will be the biggest single thing" the administration will address in the near future, says one administration official. "We're going to look at the kinds of sticky regulations that led 60,000 small businesses to drop out of offering pension plans at all. It just doesn't make sense to discourage the private sector from offering pension systems."

Of special concern will be ERISA's reporting and recordkeeping requirements. Many businessmen have charged that much of the information they must file with the government in regular reports is unnecessary and duplicative, and a real burden for the smaller companies that don't have an in-house staff of accountants and actuaries.

Also certain to be scrutinized are the maximum contribution and benefit rules that limit the amount of money an employer can put in a pension fund in one year. The limits were initially imposed to make sure pension funds were not used as a means to avoid paying taxes, because pension fund contributions qualify for handsome tax benefits.

Rules limiting the types of transactions and investments pension fund managers can make also probably will be carefully examined.

Administration officials are concerned that many of the problems lie in the law itself, and new legislation will be needed to correct many of the perceived problems.

Nonetheless, they are hopeful some changes can be made administratively, through revisions in the regulations. As a guide, they are looking at a recent article by New York attorney Alvin D. Lurie, the first person to hold the position of assistant commissioner of Internal Revenue in charge of administering ERISA.

To ease ERISA's burdens, Lurie said all Reagan "would have to do is overturn at once five rules that are causing acute pain, cancel two reporting and disclosure forms and trim five others and order immediate exemption of small business from troublesome rules in four critical areas . . ."