The invention relates to a method of detecting vitamin A in children plasma, which mainly comprises the following steps: adding 140 [mu]l of methanol and isopropanol (v/v = 8:2) to 200 [mu]l of children plasma, performing vortex for 30 s, adding 1000 [mu]l of n-hexane, performing vortex for 1 min, performing room-temperature high-speed centrifugation for 2 min (12000*g), taking 700 [mu]l of a supernatant, blow-drying the supernatant and re-dissolving the supernatant in 100 [mu]l of methanol. The chromatographic conditions include the follows: the chromatographic column is a BEHC18 column (50 mm * 2.1 mm, 1.7 [mu]m; Waters Company); the flow rate is 0.3 ml/min; a mobile phase is methanol-water (90:10); column temperature is 30 DEG C; sample size is 5 [mu]l and detection wavelength is 325 nm. A detection result proves that vitamin A chromatographic peak separation in the plasma is excellent without interference. A vitamin A curve is y=118296x+11644, wherein R2=0.9997 and recycling rate is 90-120%.