A polymer composite membrane, comprising a porous base membrane; and a heat-resistant fiber layer covering at least one side surface of the porous base membrane, wherein materials of the heat-resistant fiber layer contain a first polymeric material and a second polymeric material; the first polymeric material is a heat-resistant polymeric material whose melting point is above 180°C; and the melting point of the second polymeric material is lower than that of the first polymeric material, and a liquid absorption rate of the second polymeric material in an electrolyte at 25°C is above 40% and has an error of ±5%, wherein a weight ratio between the first polymeric material and the second polymeric material in the heat-resistant fiber layer is (0.5 to 10):1, optionally (1 to 5):1, and optionally (1 to 3):1; the first polymeric material is polyetherimide; and the second polymeric material is polyvinylidene fluoride-hexafluoropropylene; wherein the liquid absorption rate is determined by the following method: dissolving a to-be-measured material in a solvent, pouring to form a sample having a designated size, drying, then weighing the sample of a mass m1 in a glove box at 25°C full of argon, then immersing the sample in an electrolyte which contains a lithium salt LiPF 6 and an organic solvent system, the content of the lithium salt is 1 mol/L, and the organic solvent system contains 32.5 wt% of ethylene carbonate, 32.5 wt% of ethyl methyl carbonate, 32.5 wt% of dimethyl carbonate, and 2.5 wt% of vinylene carbonate by using 100 wt% of a total weight of the organic solvent system as a reference, for 24h, then taking out the sample, drying the liquid on the surface of the sample by using filter paper not performing pressing processing, weighing the sample of a mass m2, and then calculating a corresponding liquid absorption rate according to a calculation formula: " liquid absorption rate = m 2 − m 1 / m 1 × 100 % "; and wherein the heat resistant fiber layer is obtained by electrospinning. comprising a porous base membrane; and a heat-resistant fiber layer covering at least one side surface of the porous base membrane, wherein materials of the heat-resistant fiber layer contain a first polymeric material and a second polymeric material; the first polymeric material is a heat-resistant polymeric material whose melting point is above 180°C; and the melting point of the second polymeric material is lower than that of the first polymeric material, and a liquid absorption rate of the second polymeric material in an electrolyte at 25°C is above 40% and has an error of ±5%, a weight ratio between the first polymeric material and the second polymeric material in the heat-resistant fiber layer is (0.5 to 10):1, optionally (1 to 5):1, and optionally (1 to 3):1; the first polymeric material is polyetherimide; and the second polymeric material is polyvinylidene fluoride-hexafluoropropylene; wherein the liquid absorption rate is determined by the following method: dissolving a to-be-measured material in a solvent, pouring to form a sample having a designated size, drying, then weighing the sample of a mass m1 in a glove box at 25°C full of argon, then immersing the sample in an electrolyte which contains a lithium salt LiPF 6 and an organic solvent system, the content of the lithium salt is 1 mol/L, and the organic solvent system contains 32.5 wt% of ethylene carbonate, 32.5 wt% of ethyl methyl carbonate, 32.5 wt% of dimethyl carbonate, and 2.5 wt% of vinylene carbonate by using 100 wt% of a total weight of the organic solvent system as a reference, for 24h, then taking out the sample, drying the liquid on the surface of the sample by using filter paper not performing pressing processing, weighing the sample of a mass m2, and then calculating a corresponding liquid absorption rate according to a calculation formula: " liquid absorption rate = m 2 − m 1 / m 1 × 100 % "; and wherein the heat resistant fiber layer is obtained by electrospinning.