Abstract: Radiotherapy is a widely used method of cancer treatment, and quality control of radiotherapy plans relies heavily on dose verification. Traditional dose verification methods, such as ionization chambers, cannot provide high spatial resolution for 3D dose verification in the required volumes. This creates difficulties in meeting the requirements for 3D dose verification in precise dynamic radiotherapy techniques, such as IMRT, VMAT, and SBRT. In this paper, a scintillation gelbased detector was proposed as a novel solution for 3D dose verification in radiotherapy. The scintillation gel material has good properties suitable for dose measurement, including photonic soft tissue equivalence, high luminescence intensity, good dose linearity and energy response, high irradiation endurance (>1 000 Gy), and no dose rate dependence. In addition, the material’s pliability makes it a promising candidate for functional physical organ phantoms. Then, a rapid measurement device for 3D dose distribution in radiotherapy was developed, including the novel scintillation gel and a 3D optical measurement system. The 3D optical measurement system hardware consists of cameras positioned in three orthogonal views, lenses, optical mounts, reflectors, calibration boards, a light shield, and a computer. The 3D optical measurement system software includes optical simulation, image acquisition, and data processing modules. The optical simulation module uses ZEMAX software to compute the system response matrix, describe light propagation from the scintillator to the camera, and create the dose equation. The image acquisition module was implemented using MVS software. Data processing was achieved using a MATLAB-based in-house program called Gel3Ddose for data loading, image preprocessing, equation solving, detector calibration, and result analysis, which proposed the LASSO-TV model for dose equation solving. The LASSO-TV model performs total variation minimization, non-negative constraint, and noise suppression during the iterative process. The newly developed rapid 3D dose distribution measurement device was validated in clinical experiments using the Elekta Synergy linear accelerator at Shanxi Bethune Hospital. The high-resolution measurement of the 3D dose distribution inside the scintillator was achieved, and the results were compared and analyzed with the calculation data of the treatment planning system (TPS) and the measurement data of the 2D ionization chamber (MapCHECK2). The results show that in SBRT single beam irradiation, the gamma pass rate (3 mm/3%) for coronal, transverse and sagittal planes based on the treatment planning system calculation is above 90%. The dose relative error compared to the dose measured by MapCHECK2 is less than 5%, meeting the clinical dose measurement requirements set by ICRU. The developed 3D dose measurement device can provide a technical means for 3D dose verification of precision radiotherapy.