Ronald Reagan earned more than $900,000 in the last 18 months, chiefly by speaking before groups that can help his undeclared candidacy for the Republican presidential nomination, according to a financial disclosure report filed yesterday.

Republican candidates and party groups alone paid the former California governor and ex-movie star $76,942.

Reagan, who earned a total of $648,897 for making speeches, received large fees from a wide range of business and special interest groups as he tested the waters for his expected entry into the 1980 presidential race.

He also charged a total of $7,659 to speak at two Boy Scout dinners.

The disclosure reports indicate that Reagan, who has yet to formally declare himself a candidate, has a net worth and annual income matched only by fellow Republican candidates John B. Connally, the former Texas governor and secretary of the Treasury, and George Bush, former CIA director.

It is difficult to determine the precise net worth of a candidate by the reports, because income is listed by sources and in segments (for example, $50,000 to $100,000). But it appears Reagan's wealth has increased steadily since 1976 when he said his real estate and stock holdings had a total worth of $1,455,571, Bush has said his net worth is $1.8 million; Connally's is about $1.9 million.

The reports also indicate that Reagan's annual income has skyrocketed since he left office; In 1974, his last year in office, Reagan reported an income of $140,719. During the 18 months ending June 30, he reported gross income in a range between $899,860 and $1,044,359.

In addition to his speech fees, Reagan was paid $137,937 for radio broadcasts he syndicates and $30,248 for newspaper and magazine columns,

He reported a gross income of $3,500 from his ranch near Santa Barbara, interest earnings of between $2,000 and $5,999, and stock dividends of between $71,500 and $212,000.

The report was filed to meet the requirements of the new Ethics in Government Act. Although it was originally due May 15, Reagan received a series of extensions, and when it finally appeared yesterday the report was almost three months late.

Reagan's largest single holding is Rancho del Cielo, which he purchased in 1974 for $526,600. The report contained no new statement of the value of the property, but land values in the Santa Barbara area have increased dramatically in recent years.

His largest stock holding, in Continental Illinois Properties, he said is worth more than $250,000. He holds stock worth between $100,000 and $250,000 in Detroitbank Corp. of Detroit, First Union Bancorporation of St. Louis, and Western Bancorporation.

He has deposits in three Bank of America accounts totaling between $65,000 and $150,000. He has debts totaling more than $305,000;

The most controversial part of Reagan's disclosure statement is the huge fees he collected from Republican Party groups and special interest groups while deciding whether to enter the 1980 presidential race.

Traditionally, most politicians appear before party groups free, on the theory that it will build good will for themselves and strengthen the party.

Dennis Hunt, a Reagan spokesman, said yesterday that the former governor's policy is to charge a fixed fee for such appearances. The only time Reagan appears without such a fee is when he is making another speech in the immediate area, Hunt said.

Reagan charged $5,000 or more to appear before 12 different party groups during the last 18 months, He also collected $34,099 for appearing at various colleges.

The majority of his appearances, however, were before businessmen and special interest groups, including Japanese businessmen, oil interests, auto dealers, dentists, builders, food brokers, and turkey growers,

In many of the appearances Reagan gave slightly altered versions of his standard speech, which he keeps on handwritten index cards. CAPTION: Picture, Reagan's income includes $7,659 for addressing two Boy Scout dinners. AP