The substrate methionine p-nitroaniline in this paper had been used to measure methionine aminopeptidase activity.The accuracy and sensitivity of the detection were improved and the enzyme panel method was established baseed on the optimization of determination conditions,to adapt to the detection for miniaturization fermentation and the high throughput screening for high aminopeptidase-producing strains.The optimal determination conditions were as follows: 40 mmol/L ammonium chloride/ammonia buffer,pH 8.0,6 mmol/L methionine p-nitroaniline,reaction temperature 60 ℃,reaction time 10 min,measured colormetrically at 380 nm.