[en] Effects of beamlet steering and influence of total beam deflection on the injection efficiency were investigated numerically for the neutral beam injectors of large tokamaks such as JT-60. The beamlet steering by aperture displacement was investigated in the conventional two-stage accelerator by a thin lens approximation. The simultaneous displacement of apertures in the plasma and the gradient grids (or suppressor and the exit grids) turned out to be adequate for beamlet steering. This is due to that the steering characteristics scarcely depend on the field intensity ratio which determines the two-stage ion beam optics, and then the focal point does not change in the wide range of operating conditions of two-stage ion source. Beam focusing in the modified two-stage accelerator was also studied by a thin lens approximation. (auth.)