Wetting and the interaction between liquid and solid phases are significantly affected by gravity. In recent years, Chinese scientists have carried out wettability experiments in space, but the limitations of experimental facilities have hindered their ability to carry out in-situ observations of the dynamic process of wettability in space. The future Chinese space station will provide a platform for real-time observation of the melt wettability in space. To study the wettability of melt under microgravity, a research method for real-time observation on orbit is proposed. The change in the image contour is determined on the basis of Hu moments, according to changes in the image, to control the acquisition frame rate. This can greatly reduce the memory required to store the images. At the same time, the proposed method uses the binarization method to process the images, and then performs target searching and positioning. Furthermore, it uses the Canny multi-level edge detection operator to extract the target contour. The Young-Laplace equation is used to fit the contour of the droplet. Finally, it obtains the surface tension and contact angle of the melt droplet in real time. The experimental results show that the data storage capacity can be reduced by 90% nearly using this method, and the change in the contact angle and surface tension in the melting process can be obtained in real time.