Abstract: The 2-D effect and the initial energy influence of emitting electrons on space-charge-limiting current in diode are studied by PIC simulation and theoretical analysis. The space charge limited current in diode is obtained when the electrons is emitted from cathode with a initial energy. The analytic result is in good agreement with PIC simulation. Meanwhile, the 2-D effect of diode is also studied by PIC simulation, and the 2-D modified factor is obtained, which can be used in the designing and analyzing the experimental data of intense current electron beam diode.