The invention relates to a fructose sodium diphosphate oral solution and a preparation method thereof. Each 1000ml of the fructose sodium diphosphate oral solution comprises the following components: 80-120g of fructose sodium diphosphate, 0.2-0.8g of sodium pyrosulfite, 1.0-3.0g of methylparaben, 0.1-0.5g of propylparaben, 1.0-5.0g of aspartame, 0.5-3.0g of citric acid, 0.5-2.0ml of lemon essence and the balance of water; and the pH value of the prepared oral solution is adjusted to 3.6-3.8 with C100H resin. By adjusting the pH value with C1000H resin, the increase of Cl<-> and Na<+> in the solution is avoided so that the product has pure taste and proper sweetness; and through experimental confirmation, the pH value is adjusted to 3.6-3.8. Under sterilization conditions with the temperature of 105 DEG C and the time of 30 min, the product is most stable and the national drug standard is met.