The nurse supporting robot system to prepare and hand surgical instruments to a surgeon is proposed to reduce work of nurse in a surgical operation. In this paper, the surgical instrument recognition system (SIRS) is developed to hand the surgical instruments to a surgeon by the robot. The characteristics ot the instruments are area of the instruments, ratio of minimum center-contour distance to maximum one and its outline contour, are recognized by using the image processing. Kinds of the instruments are distinguished by these characteristics