The Arlington County Board yesterday adopted a $131.4-million capital improvement program for the next six fiscal years that is keyed to making improvements to existing roads, parks, schools and other facilities rather than for new projects.

"It's a planning document, but it's a reasonable guide for the staff and community to the investments we might make over the next several years," said Board Chairman John G. Milliken. "It's an example of our willingness to put money back into the community."

The capital improvement program for fiscal years 1986 through 1991, a document that will be updated and possibly revised annually, calls for almost $78.5 million of the projects to be financed by bond sales, according to Pete Eckel of the county's financial staff.

Eckel said another $38.9 million in projects would be financed on a pay-as-you-go basis, and $13.9 million would be paid for by the county's self-sustaining utilities fund.

Any bond referendums would require the approval of the County Board, which has decided to put bond issues before the voters only in even-numbered years. Thus, the next referendum would not be until fall 1986.

The capital improvement program as proposed by County Manager Larry J. Brown would fund: parks and recreation ($10.4 million), streets and highways ($22.6 million), storm drainage ($5.1 million), community conservation ($20.3 million), government facilities ($25 million), regional contributions ($2.9 million), schools ($4.3 million) and utilities ($40.8 million), some of which are financed on a pay-as-you-go basis.

Among the few specific projects included in the list are a $3 million addition to the central library and $6.5 million to purchase parkland.

The program calls for $1.5 million for improvements to the Rosslyn-Ballston high-rise corridor. The board is scheduled to decide at its July 13 meeting which projects to undertake, and is soliciting community suggestions for improvements.