The author concerns some relations between the field size and dose distribution of electron beams. The dosesof electron beams are measured by either an ion chamber with an electrometer or by film for dosimetry. We analyzesqualitatively some relations; the energy of incident electron beams and depths of maximum dose, field sizes ofelectron beams and depth of maximum dose, field size and scatter factor, electron energy and scatter factor,collimator shape and scatter factor, collimator shape and scatter factor, electron energy and surface dose, fieldsize and surface dose, field size and central axis depth dose, and field size and practical range. He meets withsome results. They are that the field size of electron beam has influence on the depth of maximum dose, scatterfactor, surface dose and central axis depth dose, scatter factor depends on the field size and energy of electronbeam, and the shape of the collimator, and the depth of maximum dose and the surface dose depend on the energy ofelectron beam, but the practical range of electron beam is independent of field size.