A method for preparing a compound of formula T-3 according to route I is disclosed. The method comprises the following steps : a first step of reacting a compound of formula T-1 with a reagent comprising a PG group in the presence of an organic base or an inorganic base, optionally under the catalysis of a catalyst, to form a compound of formula T-2; and a second step of reacting the compound of formula T-2 under the catalysis of an organic base or an inorganic base to form the compound of formula T-3. A method for preparing a compound of formula (I)-1 according to route II is further disclosed. The method comprises the following steps : step A, reacting T-3 with R-1 in the presence of a hydroxyl hydrogen removal reagent to obtain a compound of formula T-4; and step B, reacting the compound of formula T-4 under the catalysis of an organic base or an inorganic base, or in the presence of a fluorine-containing reagent, to obtain the compound of formula (I)-1. In addition, an intermediate in the above preparation methods is further disclosed.