Abstract: The accuracy and stability of the beam quality in medical linear accelerators (LINAC) are crucial for the precision of radiation therapy. This study introduces a more convenient and accurate method for quantitatively analyzing beam characteristics using the open-source Pylinac program. Beam quality information was obtained using thimble ionization chambers and electronic portal imaging devices (EPIDs). The Python-based Pylinac program was used for quantitative analysis of the absolute output dose, flatness, symmetry, and percentage depth dose curves. Furthermore, the results of the EPID analysis were compared with those of mainstream detection analysis instruments, such as MapCheck. The program was able to accurately calculate the absolute output dose and other parameters, with no significant differences observed between the results of the EPID and MapCheck (p < 0.05). The gamma (1 mm/1%) value indicated a high level of consistency between the measured curves and the model data (γ = 96.2%). Pylinac can accurately evaluate the beam quality characteristics of accelerators and can serve as a tool for daily, monthly, and annual inspections.