Abstract: Because of high integration and narrow gap between solder joints in PCBA (printed circuit board assembly) of smart phone, there is some noise in the image of PCBA inevitably and the edge of circular solder joint is obviously bonded and broken. That easily leads to the low accuracy of circular solder joint contour extraction. Therefore, an adaptive extraction algorithm of PCBA circular solder joint contour is proposed. Firstly, the guided filtering algorithm is used to effectively suppress the noise and capture the edge gradient information of circular solder joint. Secondly, the solder joint region is segmented according to the adaptive OTSU segmentation algorithm, and the contour information of circular solder joint is extracted by 8-neighborhood boundary tracking algorithm and Canny operator. Finally, the contour information is filtered by using the contour geometric characteristics of circular solder joint and the edge sliding window mechanism to obtain a finer contour of circular solder joint. The experimental results on 90 PCBA image data sets collected by the experimental equipment and three typical methods show that the accuracy, recall and F-score value of the proposed algorithm are 96.96%, 97.88% and 97.42%, respectively, and the running time is 310 ms. The contour of PCBA circular solder joint can be extracted quickly and effectively.