The director of the Office of Management and Budget yesterday announced the appointment of a chief financial officer for the federal government in a preemptive move that heads off a Senate committee that was preparing to order the same thing.

Legislation to establish a a government-wide accounting czar in the Treasury Department was introduced Wednesday by Sens. John Glenn (D-Ohio) and William V. Roth Jr. (R-Del.). But the appointment of Gerald R. Riso, who has been OMB's associate director for management, establishes the position without the need for legislation.

Riso had already been responsible for financial-management systems before his appointment as chief financial officer, a common corporate position.

Charging that the officer needed more authority and prestige to carry out his role than could be conferred by the "third or fourth level of the management side of OMB," Glenn asked whether President Reagan would make the announcement of Riso's appointment.

"The president has to announce the AIDS commission today," said OMB Director James C. Miller III.

"We wouldn't want to bog him down with too many announcements," Glenn said.

The government pours "almost $2 billion into well over 100 separate financial-management improvement projects with no central clearance or coordination," Glenn said, adding: "We know that we have at least 400 different systems in the executive branch . . . and we know that these systems rarely produce reliable, consistent information."

The chief financial officer must have clout to get departmental secretaries and their assistant secretaries to make costly and time-consuming changes, Glenn added.

"What's going to happen when the new CFO, Mr. Riso, calls up {Defense Secretary} Cap Weinberger and says we got a problem," Glenn asked Miller, "and Cap says he just gave that issue to somebody 14 levels down?"

Miller contended that Weinberger's response would be: "Gerry Riso -- my gosh, get him on the phone; I'll be right there."

Asked Glenn, "You want me to try?"

OMB Deputy Director Joseph R. Wright Jr. said Riso's new position is a kind of "comptroller of comptrollers" and is properly located in OMB. He said, in effect, when OMB calls, agencies listen. "We have no problem getting Cabinet secretaries to answer phone calls," he said. "The only way to get these management programs put in place is to tie them to the budget."

OMB has been overseeing the administration's elaborate management-improvement program, which includes efforts to upgrade the government's cash management by moving to electronic funds transfer instead of issuing tradition checks; to improve loan collection and record keeping; to increase use of credit cards; and to establish new compatible computer systems instead of continuing to use 400 different ones.

Wright denied that Riso's appointment was designed to head off Congress, saying that plans to name a CFO were included in his annual management report March 24.

Glenn argued that OMB has neither the resources nor the long-term stability of staff to handle the tasks of a CFO. "It doesn't take a mathematical genius to figure out that there have been 48 different combinations of leadership for financial management in OMB over the past seven years," he said.

Glenn added that "the force of personality of talented public managers like Gerry Riso is not enough."

Riso has been assistant secretary of the Interior, vice president of Korn/Ferry International, deputy commissioner of the Immigration and Naturalization Service and vice president of Booz-Allen & Hamilton Inc.