On the base of consciousness, the esthetic sense and the language function of shape, which had been obtained by human’s observation and the experience, a study was given to understand how does the shape play a leading role to benefit man-machine communication and expression of esthetic image in the availability design of Human-Machine interface, When the integrant parts of shape contributed to understand the function, operation, security, psychology joyful and so on aspects of the human-machine interface, the specified goals of with effectiveness, efficiency and satisfaction can be achieved in availability design to meet the people’s needs of security, amenity and pleasure. Then it pointed out that, in surface design, how to play the leading role of shape to realize and enhance the actual effect of availability design.