A now method of determing salicylic acid at carbon-fibre microelec-trode using 1. 5 order differential voltammetry is reported in this paper, the anodic current is linear with the salicylic acid concentration over the range of 5.0×10-4-7.0×10-8mol.L-1 and the detection limit is 3.5×10-8mol.L-1. It has been applied to the determination of salicylic acid in human blood and urine with satisfactory results.