This paper discusses the preliminary-announcement and display method of action and intention which is carried with a robot which moves in a human-coexisting environment. It is pointed out that the speed of motion and the direction of motion are important to announce the action of a mobile robot. The method by using blowout is proposed to tell surrounding people about these two kinds of information. Method to announce the speed of motion in translation is examined using a software simulator concerning the case that a robot is equipped with blowout, lamp, or no apparatus. Consequently, the effectiveness of the preliminary-announcement and display using blowout and the importance of information about the speed of motion are confirmed. Moreover method to announce the direction of motion in rotation is examined concerning the case to announce the target direction or the rotation speed. As a result, it is found that the target direction is efficient to announce in rotation of a mobile robot.