The Illinois Supreme Court agreed today to free Gary Dotson from prison on $100,000 bond while he appeals his 1979 conviction for a rape that his accuser now says never occurred.

His lawyer, Warren Lupel, said that he expects Dotson to be released Wednesday, when Justice Seymour Simon's two-page order is presented to the warden of the state penitentiary in Dixon.

Dotson, 28, has served six years of a 25- to 50-year sentence for the 1977 kidnap and rape of Cathleen Crowell Webb, then a 16-year-old high school student.

He was released on bond for a week last month after Webb, now a 23-year-old New Hampshire housewife, told reporters that she had fabricated the allegations out of fear that she had become pregnant by her teen-age boyfriend. Webb said she had picked Dotson's picture from some mug shots, to match her description of fictitious assailant.

But Dotson was sent back to prison after Cook County Circuit Court Judge Richard Samuels, the same judge who had tried the case in 1979, heard Webb's recantation and rejected it.

An appellate court last week rejected Dotson's request for bond. Simon ordered Dotson's release after a brief hearing today and said the high court would consider Lupel's request that it intercede in the case, bypassing the 1st District Appeals Court.

Lupel, who also has petitioned for a new trial and dismissal of the original verdict, said he was "surprised" by the speed with which Simon acted. Dotson's family has arranged a $10,000 bank loan to post the required 10 percent bond premium.

The Illinois Prisoner Review Board is scheduled to review the case Tuesday, and Gov. James R. Thompson has said that he will decide quickly whether to commute Dotson's remaining sentence by granting executive clemency.

The Cook County state's attorney's office opposed Dotson's release pending his appeals.

Assistant State's Attorney Joan Cherry argued today that "there is a very, very, very unlikely chance that the decision of Judge Samuels will be reversed. The law is very clear . . . that recantation testimony should be viewed with great suspicion . . . . "

The Associated Press reported that Illinois Department of Corrections spokesman Nic Howell said that when Dotson was told of his imminent release he responded: "Oh, fine."