The fight for control of American Finance System Inc. of Silver Spring ended yesterday.

American Finance and its corporate suitors announced a series of developments, paving the way for AFS to merge with Security Pacific Corp. of Los Angeles.

The merger still requires the approval of shareholders at the AFS's annual meeting May 24. But other potential roadblocks were removed by these actions:

Aristar Inc. of Miami said it is withdrawing its $11 per share tender offer for 47.2 percent of American Finance's common stock.

Security Pacific said it has agreed to purchase, for $9.75 a s share, the 234,100 shares (about 4.8 percent) of American owned by Aristar and affiliates of Gamble-Skogmo Inc. of Minneapolis.

American Finance said it will drop legal actions in the courts and before the Virginia State Corporation Commission aimed at blocking the threatened takeover by Aristar, which is controlled by Gamble-Skogmo.

The three-way agreement was announced jointly by the companies, ending almost four months of maneuvering.

In January, when its stock was trading at about $5 a share, AFS announced it had started merger talks again. A series of potential mergers, dating back to 1969, had produced no action.

Within a month, AFS announced tentative agreement to with Security Pacific, the nation's 11th largest bank holding company, the parent of Security Pacific National Bank. Security offered a tax-free exchange of stock, worth $7.85 per share of AFS.

Before that deal could be consumated, Aristar made a $9.50 cash offer for the Silver Spring company, which operates a chain of about 370 consumer finance offices. Aristar and AFS had held unfruitful merger talks in 1975, and Aristar and its parent and purchased a block of AFS stock.

In a later round of bidding, Aristar raised its cash offer to $11 a share, and Security Pacific offered a tax-free exchange of stock worth $10. That offer will be voted on by AFS share-holders and if approved it will be submitted to regulatory agencies for their review.