The Drive Beam Linac has to accelerate a 4.2 A electron beam up to 2.4 GeV in almost fully-loaded structures. The pulse contains more than 70000 bunches, one in every second RF bucket, and has a length of 140 µs. Such high bunch charge with high repetition rate brings up beam instability along the beamline. We represent different options for the lattice of the linac with comparison of transverse instability for each, and longitudinal stability is discussed for different bunch compressors. Finally beam alignment results is represented for the selected lattice.