This work aims to investigate major operation parameters including scan uniformity, film orientation, scan resolution, image region of interest, energy dependence, postirradiation coloration, and ambient temperature in order to establish an appropriate protocol for calibration and dose measurement using a GafChromic film dosimetry system. A two-dimensional dosimetry system comprising GafChromic films and an Epson Expression 1680 flatbed document scanner was employed. EBT films in a 30- × 30- × 25-cm3 solid water phantom were exposed in a photon field delivered by a Varian 21EX electron linear accelerator with a 10- × 10-cm2 field size. The operation parameters of the GafChromic film dosimetry system were investigated in detail. The dose profile measurement was compared with calculation delivered by the Varian Eclipse treatment planning system. Some deviations in the penumbra regions were found.