Visual flow measurement technology has important application value in non-contact river flow monitoring. By reviewing the main methods of visual current measurement algorithms, including optical target tracking current measurement algorithm and statistical feature current measurement algorithm, the underlying principles and research status of these two methods are analyzed in depth. The problems existing in the existing visual flow measurement algorithms are discussed, such as the unsatisfactory measurement accuracy of the algorithm in dealing with the irregularity of natural rivers, complex flow characteristics and field environmental interference, and the optical target tracking flow measurement algorithm and the statistical feature flow measurement algorithm are compared and analyzed. Finally, the advantages and disadvantages of these two methods are summarized, and the future research directions are prospected.