This is one in a series of articles on President Reagan's fiscal 1986 budget proposals.

Although Reagan's budget calls for some of the Small Business Administration's functions to be transferred to the Commerce and Treasury departments, more than 2,000 SBA employes could lose their jobs by December.

Under the president's plan, the agency would spend the first quarter of fiscal 1986 shutting down. The plan, however, won't be enacted unless approved by Congress, and members involved in small-business issues oppose the idea.

SBA Administrator James C. Sanders told senior staffers in a memo this week that the proposal is crafted "to eliminate SBA's credit programs and transfer most non-credit activities" to the other agencies. The government would save $3.5 billion if the agency made no loans in fiscal 1986.

The $300.1 million that the SBA plans to spend in fiscal 1985 on salaries and administrative expenses would be transformed next year into a $73.96 million line item at Treasury and $52.91 million at Commerce. The agency would spend $97.1 million in the first quarter as it wound down its operations.

The biggest group of employes -- 915 -- would move to Treasury to monitor the sale of $10 billion in outstanding business loans and $6 billion in outstanding disaster-assistance loans.

The budget also calls for:

* Saving $344 million by ending virtually all management-assistance programs for small businesses. In the transition quarter, SBA would spend $85.8 million.

* Transferring procurement-assistance programs to Commerce. The minority-aid program would be merged with the Minority Business Development Agency and funded at the fiscal 1985 level of $318.1 million. Funds for small business set-aside programs would increase by nearly 30 percent above fiscal 1985 levels, primarily because of a new law requiring some military installations to divert more contracts for spare parts to small firms.

* Saving $32 million in management and administration costs and $20 million in field operations. Sanders, in his memo, said no decisions have been made on the field structure for programs that would be transferred.