State governments finished fiscal year 1984 with $6.3 billion in surplus funds, most of which was concentrated in a few state treasuries and leaves a majority of states vulnerable to proposed cuts in federal aid, the National Governors' Association reported yesterday.

Tax cuts and an anticipated economic slump are expected to lower the surplus to $5.3 billion by the end of the current state fiscal year June 30, and President Reagan has proposed a $7 billion reduction in aid to state and local governments for the federal fiscal year that begins Oct. 1.

"If that takes place, it would clearly wipe out most of that surplus," said Raymond C. Sheppach, executive director of the association.

Released at a news conference, the report was an update of an annual survey of state governments conducted by the governors' association and the National Association of State Budget Officers.

The $6.3 billion surplus was equal to 3.9 percent of the states' aggregate budgets, less than half of the surplus levels of 1979 and 1980 and well below the 5 percent figure that Sheppach said Wall Street analysts consider a "reasonable" sign of health for state economies.

Eight states held about half of the $6.3 billion surplus, and five states will hold about half of the $5.3 billion 1985 surplus, Sheppach said. The states in best fiscal health seemed to be those in the Great Lakes and mid-Atlantic regions.

Meanwhile, energy-producing states are expected to suffer from drops in oil prices, while farm states and mineral states have not recovered from the economic recession.

"We're not out of the woods yet," Sheppach said.

The report also said 14 states have proposed tax cuts for fiscal year 1986, while 17 are considering tax increases. But the aggregate amount of money from anticipated tax reductions is $1.1 billion more than the additional revenues of expected tax boosts, Sheppach said.

Compared with 1981, he said, net state spending will be 2 percent higher in 1985, as against an 11 percent increase for the federal government during the same period.

The survey reported Maryland's surplus as $18 million for 1984 and an estimated $15 million for 1985. Figures for Virginia were $81 million in 1984 and $86 million in 1985. More recently, Maryland officials have projected a surplus of at least $47 million for 1985.