Abstract: This paper proposes a Built-In Self-Test approach able to detect and accurately diagnose all single and practically all multiple faulty configurable logic blocks (CLBs) in Virtex-4 FPGA with better diagnostic resolution.Unlike conventional BIST, the method proposed could detect and locate multiple fault CLBs concurrently.Based on the location of the fault CLBs, we could also identify their internal faulty modules or modes of operation.For the completion of fault testing, a testing program is developed.The testing result shows that the method proposed could accurately detect and locate the fault CLBs.This kind of method is easily scalable to other SRAM FPGA with similar architecture.