Abstract: The thermoluminescence (TL) response characteristics of hot-pressed CaF₂:Mn (TLD-400) chip at high dose level were experimentally studied by using ⁶⁰Co isotope sources, and the high dose response curve of CaF₂:Mn chip was obtained to meet the requirements for determining absorbed dose in the radiation-hardness test of electronic device. Irradiation experiment was performed on two sets of ⁶⁰Co gamma irradiation facilities delivering the dose rate with 21.38 Gy/h and 945.5 Gy/h in State Key Laboratory of Intense Pulsed Radiation Simulation and Effect (SKLIPR) of Northwest Institute of Nuclear Technology (NINT). A 0.6 cm³ ionization chamber traced was used to measure the dose rate of gamma irradiation field. The study result shows that the typical TL glow curve of CaF₂:Mn chip at high dose level is a composite of several overlapped components, with maximum intensity appearing around 260 ℃. The actual shape of TL composite peak depends on the irradiation dose. Using the dynamic distribution points, the high dose response curve with high accuracy in the range of 1-3 500 Gy under slow heating rate was presented, which consists of two linear regions (1-500 Gy, 500-2 200 Gy) and one saturated region (2 200-3 500 Gy). In the range of 1-500 Gy and 500-2 200 Gy, the TL response increases linearly with irradiation dose, and the linear correlation coefficients (R²) are better than 0.99. But there is a great difference as large as nearly five times in the two slopes of linear range. Besides, the TL response increases no longer with increasing irradiation dose in the range of 2 200-3 500 Gy, and the saturated threshold is 2 200 Gy, which is far below the manufacturer’s nominal upper limit of 2 600 Gy. Moreover, there is no sublinear region or superlinear region before saturation, which is different from the literatures reported. The TL response per Gy increases considerably, reaching its maximum at 400 Gy, and then decreases with increasing dose. The uniformity and reproducibility of CaF₂:Mn chip TL response were further evaluated. The standard deviation of 30 random thermoluminescence dosimeters (TLDs) irradiated at 50 Gy and ten repeated measurements in the identical condition at 1 000 Gy are 3.8% and 0.47%, respectively. The TL intensity of the chip stored in darkness at room temperature declines within 1% in two weeks and 4% in three weeks, respectively, which indicates that CaF₂:Mn chip has excellent storage stability. After being irradiated at a saturated dose of 3 000 Gy, the TL intensity of the chip in the dose range of 500-2 000 Gy decreases by 3%-9% compared with that before saturation, and the response performance fails to restore by thermal annealing, which implies the onset of gamma radiation damage and the damage dose of about 3 000 Gy. The result provides a new reference for the application of CaF₂:Mn phosphor in measuring absorbed dose of electronic device in radiation-hardness test.