Abstract: Energy deposition of a normally incident 0-5MeV electron beam in KrF laser media was simulated using Monte carlo method, a periodic boundury condition was used along the laser axis.The spatial distributions of energy deposition both parallel and perpendicular to electron beam were obtaned The continue -slow-down approximation was adopted for energy losses of electrons,and Goudsmit-Saunderson angle distribution theory was used to calculate themulti-scattering angle distribution of the incident electrons. The laser medium contains 89.6% of Ar, 10% of Kr and 0.4% of F₂.Because the component of fluorine was very small, the energy deposited in flourine was neglected. The total deposited energy in the laser medium with 0.001813g/cm³ density was about 4.34% of the initial energy; 0.003658g/cm³ density, 9-11%; 0.001813g/cm³ density. 11.53%. Meanwhile the angle distributions of outgoing electrons scattered through Kr and Ar with different densities were also obtained. The computed results of electron deposition in semi-infinite Al target were consistent with those of ONETRAN code and experiment results.