Abstract: Effects of electron beam parameters,including radius,emittance and en-ergy, on bremsstrahlung exposure are discussed in this paper.It is shown that, in fixed beam radius,the larger the beam emittance,the smaller the exposure X₁at 1m in front of the target,and that in fixed emittance,the exposure quickly increases when the beam radius increases from 0 to R_bm then it slowly decreases as the radius becomes large fur-ther.Effects of them on angular distribution of the exposure are also exposed. Because of using K-V beam distribution,the results for X₁ are conservative,