At-speed current testing is a novel method to test digital circuit. This paper is an experimental research for at-speed current testing to be applied to AT89C51 microprocessor. To make the test process feasible, some instruction sequences are carefully selected to let them be able to execute repeatedly by the microprocessor, and the average current consumed by AT89C51 is then measured with a simple current meter. Test generation for the instruction sequence is presented. Experimental results show that the instruction level at-speed current testing technique is feasible for and applicable to AT89C51 microprocessor testing.