Former vice president Walter F. Mondale yesterday denounced President Reagan for having "slapped . . . in the face" the National Commission on Education, and proposed a five-point, $11 billion-a-year program for meeting the panel's goals of improving the nation's educational system.

"Without educational excellence, the billions we spend on the military are often wasted, because our security depends on our intelligence," Mondale said at Harvard University's John F. Kennedy School of Government.

" . . . Yet in answer to the commission's . . . impassioned plea for educational excellence, Mr. Reagan proposes to dismantle the federal effort. That is an outrage," said Mondale, a leading candidate for the Democratic presidential nomination.

Mondale's proposal, fully funded, would cost $11 billion a year. That price tag, and the harsh partisan rhetoric that came with it, may help make improving education in America into a major presidential campaign issue.

The centerpiece of Mondale's plan is a $4.5 billion-a-year "fund for excellence" that would provide block education grants for communities to use as they see fit, from improving math and science labs to raising teachers' salaries to developing computer technology courses.

The Mondale plan would be the sort of block grant favored by Republicans in past years. It calls for each community to create its own commission on excellence in education to design its own program.

Mondale's plan also calls for:

* An "Education Corps" and other programs, costing a total of $1 million, to encourage more talented students to become teachers; student loans would be forgiven for graduates who spend four years teaching critical subjects such as math, science or languages.

* A $1 billion allocation to modernize and strengthen science and research facilities and programs.

* Increases of $3 billion in programs for disadvantaged and minority students, including Title I, bilingual education, Talent Search and Upward Bound.

* Student aid programs, funded at $1.5 billion, designed to help students from low-and moderate-income families go to college.

Two weeks ago, the education commission called on the federal government to provide the leadership to "help fund and support" efforts to halt the decline in education it said is threatening the nation's future. The president responded by saying that money would not solve America's education problems, but that voluntary school prayer and abolishing the Department of Education would be steps in the right direction.

"Our educational system is in the grip of a crisis caused by low standards, lack of purpose, ineffective use of resources and a failure to challenge students . . . to the boundaries of individual ability," the president said then. "We'll continue to work . . . for passage of tuition tax credits, vouchers, educational savings accounts, voluntary school prayer and abolishing the Department of Education."

Reagan expanded on those comments a few days later, saying:

"There are things the federal government can and must do to ensure educational excellence. But bigger budgets are not the answer. Federal spending increased 17-fold during the same 20 years that marked such a dramatic decline in quality."

As Mondale sees it, when the commission members handed the president their recommendations, "Mr. Reagan slapped them in the face . . . . Two weeks ago, the nation turned to Mr. Reagan. Two weeks ago, he turned his back on the country, its children, and its future. Those are tough words, but I believe them."

All six Democratic candidates for president take a similar line on the question of how to improve education. Sen. Gary Hart (D-Colo.) has introduced the American Defense Education Act, which is championed by the National Education Association.

Education Secretary Terrel H. Bell took issue with Mondale's plan.

"I'd rather see the states do it," he said. "But if I were to spend $11 billion in federal money, I'd want to concentrate it on one area rather than spread it out over five areas . . . , which just dilutes its effectiveness.

"We have such an acute problem in the area of math and science, for example, that I would rather see the money spent just in that one area."