A galactose oral composition having galactose, an antioxidant and a buffer. The galactose oral composition contains 1%-80% by weight of galactose. The antioxidant is selected from Vitamin A, Vitamin C, Vitamin E, Ethylenediaminetetraacetic acid (EDTA), sodium bisulfite, flavonoids, polyphenols, Diethylenetriaminepentaacetic acid (DTPA), and NTA-Nitrilotriacetate acid (NTA). The buffer is selected from ascorbic acid buffer, citrate buffer, phosphate buffer, acetate buffer, carbonate buffer, and triethanolamine buffer. The galactose oral composition can be applied to detect individual galactose metabolic ability to assess liver function.