Spray field of the shower nozzle has the characteristics of speediness and instantaneity. The interaction among particles in droplet segment and atomization section makes the direction of movement complex and the profile of the image principal part area unclear. It is difficult to divide the images into principal part and background. Lots of threshold segmentation technologies used recently can’t receive satisfied result in the image process of shower nozzle spray field. Therefore, this article proposes a new extracting technology to extract the threshold automatically based on Otsu Method, which uses absolute value to calculate the average gray gap between section and overall and find the suitable threshold. The result of binarization segmentation by this threshold shows that it can express the characteristics of water jets completely and reduce information losing.