A polyester resin composition, comprising a high-acid-value carboxyl-terminated polyester resin and a low-acid-value carboxyl-terminated polyester resin, wherein: the high-acid-value carboxyl-terminated polyester resin has an acid value of 75 mgKOH/g to 90 mgKOH/g, a melt viscosity of 2,000 mPa•s to 6,000 mPa•s at 200°C, and a glass transition temperature of 55°C to 62°C; and the high-acid-value carboxyl-terminated polyester resin is prepared from the following raw materials in percentage by mass: 26% to 46% of polyol, 0.2% to 6% of branching agent, 45% to 70% of polyacid, 0.1% to 3% of partially carboxylated benzophenone compound, 5% to 18% of acidolysis agent, 0.05% to 0.25% esterification catalyst, 0.06% to 0.3% of heat stabilizer, and 0.2% to 1.2% of antioxidant; the low-acid-value carboxyl-terminated polyester resin has an acid value of 30 mgKOH/g to 37 mgKOH/g, a melt viscosity of 2,000 mPa•s to 7,000 mPa•s at 200°C, and a glass transition temperature of 51°C to 60°C; and the low-acid-value carboxyl-terminated polyester resin is prepared from the following raw materials in percentage by mass: 34% to 57% of polyol, 0.1% to 2% of branching agent, 43% to 65% of polyacid, 0.1% to 3% of partially carboxylated benzophenone compound, 2% to 10% of acidolysis agent, 0.05% to 0.25% of esterification catalyst, 0.06% to 0.3% of heat stabilizer, and 0.2% to 1.2% of antioxidant; the acid value is tested according to GB/T 6743-2008; the melt viscosity is tested according to GB/T9751.1-2008; and the glass transition temperature is tested according to GB/T 19466.2-2004; and the partially carboxylated benzophenone compound is prepared by a preparation method comprising the following steps of: adding 2,2',4,4'-tetrahydroxybenzophenone and a mixed solvent of N,N-dimethylformamide and tetrahydrofuran into a reaction kettle under protection of protective gas, keeping a reaction temperature at 20°C to 25°C, slowly adding sodium hydride, then adding a tetrahydrofuran solution of pyromellitic anhydride when there are no bubbles generated, reacting at 20°C to 25°C for 3 hours to 8 hours, adjusting a pH value to 4 to 5, extracting, washing with water and drying to obtain the partially carboxylated benzophenone compound. the high-acid-value carboxyl-terminated polyester resin has an acid value of 75 mgKOH/g to 90 mgKOH/g, a melt viscosity of 2,000 mPa•s to 6,000 mPa•s at 200°C, and a glass transition temperature of 55°C to 62°C; and the high-acid-value carboxyl-terminated polyester resin is prepared from the following raw materials in percentage by mass: 26% to 46% of polyol, 0.2% to 6% of branching agent, 45% to 70% of polyacid, 0.1% to 3% of partially carboxylated benzophenone compound, 5% to 18% of acidolysis agent, 0.05% to 0.25% esterification catalyst, 0.06% to 0.3% of heat stabilizer, and 0.2% to 1.2% of antioxidant; the low-acid-value carboxyl-terminated polyester resin has an acid value of 30 mgKOH/g to 37 mgKOH/g, a melt viscosity of 2,000 mPa•s to 7,000 mPa•s at 200°C, and a glass transition temperature of 51°C to 60°C; and the low-acid-value carboxyl-terminated polyester resin is prepared from the following raw materials in percentage by mass: 34% to 57% of polyol, 0.1% to 2% of branching agent, 43% to 65% of polyacid, 0.1% to 3% of partially carboxylated benzophenone compound, 2% to 10% of acidolysis agent, 0.05% to 0.25% of esterification catalyst, 0.06% to 0.3% of heat stabilizer, and 0.2% to 1.2% of antioxidant; the acid value is tested according to GB/T 6743-2008; the melt viscosity is tested according to GB/T9751.1-2008; and the glass transition temperature is tested according to GB/T 19466.2-2004; and the partially carboxylated benzophenone compound is prepared by a preparation method comprising the following steps of: adding 2,2',4,4'-tetrahydroxybenzophenone and a mixed solvent of N,N-dimethylformamide and tetrahydrofuran into a reaction kettle under protection of protective gas, keeping a reaction temperature at 20°C to 25°C, slowly adding sodium hydride, then adding a tetrahydrofuran solution of pyromellitic anhydride when there are no bubbles generated, reacting at 20°C to 25°C for 3 hours to 8 hours, adjusting a pH value to 4 to 5, extracting, washing with water and drying to obtain the partially carboxylated benzophenone compound.