High-sensitivity and wide-linear-range thermoluminescence dosimeter (TLD) is of importance for detecting high-dose radiation in industry, medicine, and agriculture as well as materials and food processing. In this work, we synthesize a series of LiMgPO4 doped with Tm3+, Tb3+, and B3+ via a high-temperature solid-state reaction technique. To observe the effect of dopants, we first investigate the structure by Rietveld refinement of high-quality X-ray diffraction (XRD) data and then study the thermoluminescence (TL) properties of samples radiated by beta-rays in detail. The TL signal of LiMgPO4:Tm,Tb,B is originated from Tm3+ 4f-4f transitions. The kinetic parameters are obtained through fitting the TL glow curve based on the general-order kinetics model, revealing that the dominant TL peak at similar to 323 degrees C is related to similar to 1.49 eV trap. Through constructing the vacuum-referred binding energy (VRBE) scheme, we uncover that this deep trap mainly originates from the Tb-3(+) dopant acted as the captured center of free hole. After codoping 0.6% B-3(+), the sensitivity of sample as TLD increases similar to 170%. According to the radiation dose-dependent TL intensities, the sensitivity of LiMgPO4:Tm,Tb,B is about 200% larger than that of the commercial LiF:Mg,Cu,P at 0.08 Gy, and more sensitive at higher dose. Moreover, the studied sample has wider linear range (up to 10 000 Gy) toward high-dose side, good reproducibility (RSD similar to 4.6%), and weak fading (similar to 8% after 34 days), and therefore has potential application as TLD for monitoring high-dose radiation.