An Alexandria federal grand jury yesterday charged a Silver Spring businessman with mail and tax fraud in connection with a scheme in which he allegedly took more than $87,000 from immigrants after promising to set them up in small businesses.

The 21-count indictment against Geary Stephen Simon, 32, alleges that he represented himself as the head of a firm that would set up small retail businesses such as restaurants, newspaper stands and ice cream shops in exchange for a fee from the purchaser.

Simon instead diverted the money he received to his "personal benefit, to the detriment of the purchasers," the indictment alleges, whom he "would purposely cultivate . . . because of their lack of business sophistication."

In addition to mail and tax fraud, Simon was charged with making false claims, interstate transportation of stolen property, obstruction of a criminal investigation and obstruction of justice. The indictment alleges Simon told a witness before the federal grand jury he would "get her" if she testified against him.

Simon could not be reached for comment. A bench warrant was issued yesterday for his arrest and he is scheduled to be arraigned April 1.

According to the indictment, Simon, using aliases, variously claimed to be chief executive officer, vice president and general counsel of Commerical Development and Finance Corporation, which also had offices in Carson City, Nev.

Between July l979 and August l981 Simon attempted "to create the image that CODECO" was a large corporation "with millions of dollars in assets, offices located throughout the United States and dozens of employes," the indictment states.

Simon approached 25 people, most of them new immigrants, and promised to set them up a fully equipped businesses that included a carry-out shop, a wine and cheese shop, and a clothing store, according to the indictment. In all, he collected more than $87,000 from the would-be new retailers, it said.

In l981, Simon was arrested by Arlington police and charged with grand larceny for allegedly cheating a Turkish immigrant in a fraudulent business deal. Assistant U.S. Attorney Lawrence J. Leiser said Simon was tried and acquitted of those charges in Arlington Circuit Court.

Simon was also the object of at least seven civil suits in l980 and l981 that sought the recovery of money and damages.