Based on a sample of broadband amplifier of TI OPA691,this paper studies the self-excited oscillation phenomenon which caused by the driving cable length. This paper analyzes the affection of the self-excited oscillation and builds a model to explain this phenomenon. Finally, this paper comes up with an effective design method to eliminate the self-excited oscillation. So it provides a reference for eliminating the self-excited oscillation in the broadband amplifier circuits.