Abstract: Following a previous article in which identification of drill-string system with white noise as input signals was discussed,this work investigated the characteristics of pseudo- random signals and ways of generating pseudo-random signals. The results show that the input white noise can be substitute by pseudo-random signals in identifying the impulse response of a
drill-string system. Using input signals, and output signal, the impulse response of drill-string is obtained. Some impor-tant aspects of drilling engineering, such as critical rotation speed of drill-string, drill-string resonance, interactions be-tween the drill string and the borehole wall and lithology of the formation drilled, are discussed.

Key words: pseudo-random signal, drill stem, impulse response, identification