Under ultrasonic dispersing, an ionic liquid-based nanofluid was prepared by extraction-reduction method using 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIm][PF6]) as medium, poly(vinylpyrrolidone) as an extractant and a dispersant, and gold nanoparticles (AuNPs) as nanoparticles. A new electrochemical sensor for detecting uric acid (UA) was fabricated by immobilizing the ionic liquid-based nanofluids containing AuNPs on a glassy carbon electrode surface. This sensor exhibited good selectivity, reproducibility, and sensitivity for the direct determination of UA in real human urine samples.