Improvisation is sometimes hard to be defined. Every theater worker has their own concept, methode and way to do it. But must of all, improvisation is always connected to spontanity which is transformed from acting is doing. When acting is reality of doing there would be a physcal action which brings influence to feelings or emotions. To have a spontaneus physical adaptation in every beat of scene of acting, actors should be well trained in the term of improvisation. The training materials of improvisation contains all elements of acting which are following four rules; why, do’s, don’ts, and how. Actors whom have skill of improvisation could bring it into the reality of acting as a technique in script’s based theater or to perform within improvisation’s theater. Keywords; improvisation, acting technique, performance, training