The House of Representatives is expected to take up a bill to revamp federal regulation of the nation's airline industry today more than four months after it was approved by the House Public Works and Transportation Committee.

The measure is intended to reduce the role of the Civil Aeronautics Board in the fare and route decisions of the airlines, whose managements would have increasing freedom during a transition period to test their ideas in the marketplace and let consumers decide on their fate.

The pending House measure actually would abolish the CAB at the end of 1982, transferring only subsidy, international and antitrust functions to other federal departments.

Several key provisions, however, are drafted in amore conservative manner than those of a Senate-passed measure, and would move the industry from its highly regulated past to a more competitive environment at a slower pace than the current CAB has been moving.

Although the bill is expected to pass, supporters are worried that a House-Senate conference might not be able to hammer out a compromise before congressional adjournment, scheduled for early October. The Senate bill passed by an 83-to-9 vote in April.

The House measure would:

Give the CAB a new policy statement, with a greater emphasis on competition, to guide its policy-making.

Give the airlines limited authority to enter new routes without CAB approval. Each airline could add a route next year and protect one existing route from new competition. The CAB then would study the results and recommend to Congress any further free-entry authorization.

(The Senate bill would allow each airline to add one route a year for two years and two routes a year after that without CAB interference, also with some built-in protections.)

Allow the airlines easier access to routes where carriers have not been using existing authority.

Grant the airlines more flexibility to lower fares without CAB approval. An airline would be able to cut its, fares 25 percent the first year and another 25 percent the second year. It would be able to increase fares up to 5 percent without approval only following release of the CAB study on route entry and congressional response to it.

(The Senate bill would allow fare reductions of up to 35 percent and increases of up to 5 percent on nonmonoply routes. The CAB itself already has allowed airlines to lower fares by up to 70 percent without prior approval, and to raise fares by up to 10 percent, and to raise fares by up to 10 percent, depending on the amount of competition on each route.)

Impose procedural deadlines on the CAB for making major decisions affecting the airlines and simplify board procedures of less-controversial proceedings.

Like the Senate bill, the House measure also guarantees small communities air service for 10 years and makes commuter airlines eligible for federal subsidies to serve those points. Commuter airlines also would be allowed to fly larger airplanes than they can now.

Several attempts are expected on the floow both to strengthen and weaken the procompetitive thrust of the bill. Rep. Allen E. Ertel (D-Pa.) and 10 others are sponsoring one amendment under which airlines seeking to block potential competitors' would have to prove that the new service is not consistent with the public interest. The Senate adopted a similar amendment.

Another Ertel amendment would increase the amount of automatic new routes airlines could enter, while another amendment floating around would end the board's current practice of giving airlines "permissive" authority to begin service on new routes - or not being it - market conditions dictate.