The class rooms for vocal music lessons at the college of music should be prepared with acoustic performance having similar quality to a real theater. However, most of domestic music colleges used too many sound absorbing materials, so that a sound is too dry and poor, which makes a singer to increase the sound level. Furthermore, because of this acoustic characteristics, at a theater a singer comes to hear a total different sound of his own song. For this, students and professors are in trouble during a lesson. At the study from this point of view, the finishing materials were changed to have the best sound condition by site measurement and acoustic simulation. It is assumed that the study result above will be used as an effective document to improve acoustic performance. Keywords：Acoustic Simulation, Impulse Response, Acoustic Characteristics.