Abstract: Preparation method of fosamprenavir derivatives is disclosed. The compound shown by formula II or its ammonium salt is reacted with a metal ion source in solvent to obtain the compound shown by formula Iii. After isolating and purifying, the compound shown by formula III is catalytically reduced to the compound shown by formula I. In the formula, X is metal ion. Preferably, the metal ion source is a calcium ion source, sodium ion source, or potassium ion source, and X is calcium ion, sodium ion, or potassium ion. The solvent is methanol, ethanol, n-propanol, isopropanol, n-butanol, or sec-butanol. The catalytic reduction is carried out by using hydrogen as a reducing agent in the presence of palladium on carbon catalyst. The ammonium salt is methylamine salt, dimethylamine salt, ethylamine salt, diethylamine salt, isopropylamine salt, dibutylamine salt, dipropylamine salt, t-butylamine salt, or dicyclohexylamine salt.