Tilting against the Reagan administration's policy of curbing federal land acquisition, a Republican senator yesterday introduced a bill that would set aside $1 billion a year to buy more land for recreation and conservation purposes.

Sen. John H. Chafee (R-R.I.) said a fund dedicated to land purchases was needed because open space is disappearing at an "alarming rate" under pressure from developers.

The bill mirrors a recommendation by a presidential panel on outdoor recreation, which urged President Reagan this year to support a $1 billion-a-year trust fund to buy recreational land.

The proposal got a cool reception at the White House, which has repeatedly sought to eliminate funds for federal land purchases.

Chafee's proposal for financing the trust fund is likely to be no more popular: The bill calls for a national real-estate transfer tax of as much as 2.5 percent on transactions of $5 million or more, aimed at raising $500 million a year.

Chafee said $300 million more would be earmarked from royalties on federal offshore oil and gas leases and $200 million would be raised by issuing special conservation bonds.

Nearly $800 million a year from oil and gas revenues now goes into a Land and Water Conservation Fund, but less than half that amount has been appropriated to buy land in recent years.

Chafee said his bill would assure that the funds could not be "raided" for other purposes.

The bill calls for 40 percent of the funds to go to the federal government, which has a $2 billion-plus backlog of land acquisitions that have been authorized by Congress but never completed.

Most of that land is in, or adjacent to, existing national parks, refuges and wilderness areas.

State and local governments would get 55 percent to be used as for matching grants to buy or rehabilitate recreational areas. The remaining 5 percent would be used to finance a National Endowment for the Preservation of Open Space patterned after the National Endowment for the Arts and aimed at encouraging private conservation efforts.

Chafee said he anticipated opposition from developers, but that he hoped real-estate interests would recognize that parks and open space "add an appealing dimension to their own projects."