FLASH radiotherapy delivers the entire dose to the target area within milliseconds using ultra-high dose rates, rendering existing online dosimeters essentially ineffective. Currently, radiation-sensitive films are commonly employed for dose measurement. Utilizing an electron accelerator developed by the Institute of Applied Electronics of CAEP, an electron FLASH radiotherapy platform was established to investigate the dose rate range and dose distribution using the EBT3 film’s rapid readout method. Experimental results indicate that the rapid readout method of EBT3 films is applicable for dose measurement in electron FLASH radiotherapy, with dose rates ranging from 240 Gy/s to 290 Gy/s at a source-to-skin distance of 100 cm and a depth of 1 cm. Fluctuations in the average energy of the electron beam reaching the surface of the phantom result in dose fluctuations of approximately ±5% in the target area. The surface dose distribution meets the requirements of flatness within ±5% and symmetry within ±3%.