In order to accelerate the development of microfluidic technology,it is more and more urgent to detect the motion state of fluid in microchannel in real time and accurately.Aimed at the problem that current microfluidic technology cannot effectively solve,a real-time tracking algorithm based on LK optical flow method was proposed,which can effectively detect the subtle movement of fluid in microfluidic.Firstly,captured the required image frames in the real-time video sequence,selected the ROI area and grayscale the image,the image was filtered by Gaussian.Then divided the grid and calculated the optical flow field with LK optical flow method,the independent optical flow vectors were filtered by threshold segmentation.Finally,the remaining optical flow vector was converted into two real value images and the pixel distance was calculated,the motion speed of the target can be calculated by the time difference between the image frames.The experimental results show that standard deviation of the measured velocity σ<1.The method can track the moving liquid in real time with high accuracy and efficiency.