For the problem that image segmentation link of steel tube recognition and counting system is affected easily by uneven illumination, and deficiency that some objects’ mistaken segmentation is caused by segmentation after image’s enhancing, a multi-threshold S-F (Segmentation-Fusion) image segmentation method is proposed. According to improved Otsu multi-threshold method, the morphology algorithm and image fusion technology are applied to extract steel tube objects. Experimental results show that the steel tube image segmentation effect of this method is obviously superior to traditional methods’ under uneven illumination circumstance, and the proposed method is free of the effect of illumination quality and well-adapted, which can be applied in objects recognition of the machine vision field.