This study aims to evaluate the dosimetric characteristics of electron FLASH-RT by combining experimental measurements with numerical simulations. In the experiment, EBT3 films were used to measure doses in solid water phantoms, while the MCNP5 program was employed to simulate and verify beam characteristics. The experimental platform was constructed based on a 9 MeV electron linear accelerator, and by adjusting the accelerator parameters, an ultra-high dose rate of 250 Gy/s was achieved at a source-to-surface distance of 1 m. The maximum deviation between experimental and simulated results in dose distribution did not exceed 5%, and the beam flatness was controlled within 3%. Key dose rate assessments show that the accelerator can work at maximum conditions to achieve the ultra-high dose rate required for the FLASH effect. Off-axis dose variation studies indicate that the presence of a water layer in the extraction window improved the uniformity of the beam. Central axis depth dose distribution analysis showes that the simulation and experimental results matched well at a water layer thickness of 10 mm. The two-dimensional dose distribution showes that the simulation results are consistent with the EBT3 film measurements. The study results demonstrate that the electron FLASH-RT experimental platform can provide the required ultra-high dose rate, and there is a high degree of consistency between experimental and simulation results, providing important dosimetric parameters and beam characteristic references for further research and application of FLASH-RT.