A robot control system comprises the components of a photographing image acquiring part which acquires a photographing image; and a control part which controls a robot according to the photographed image. The photographing image acquiring part acquires the photographing image which contains an assembling object and an assembled object of an assembling operation, at least the assembled object. The control part performs characteristic quantity detection on the assembled object according to the photographing image and makes the assembling object move according to the characteristic quantity of the assembled object.