The Xray image of BGA has low SNR characteristic and nonuniformity characteristic. Traditional threshold segmentation is unable to segment BGA solder from background accurately. By analyzing of the histogram of the BGA Xray image, Wiener filtering was used in the image preprocessing procedure. The filter parameter was adjusted for different images. Low and high smooth operations were used in minor and bigger differences, respectively. OTSU method was implemented to select a initial threshold, and an improved threshold segmentation algorithm was used to segmented images based OTSU method. It meaned that the BGA image would not be processed directly by OTSU method. In fact, a better threshold would be found by calculating the mean value and calculating the max statistic of pixels. A new pixel value was chosen to replace all pixels value of the background in BGA image. The experimental results show that this algorithm improves the segmented effect compared with the traditional OTSU method.