Abstract: The liquid experiment in space needs intelligence to deal with the surveillance image right away to obtain the goal parameters. A method is investigated to analyze the physical feature of a drop, such as surface tension, contact angle and volume through fitting contour of the drop picture. From the grey picture, generally contour of a drop is obtained by edge detection and segmentation algorithms. Constructed the Laplace equation of the drop, made contour approach process through comparing and using Newton-Raphson method, Runge-Kutta method and coordinate optimizing method. With the help of contour approach, physical feature of the drop is obtained. A new algorithm which nests Newton-Raphson method with One-dimensional optimization is presented. Compared with the original algorithm raised by Ref.\,[1], the new one reached convergence quickly with high accuracy. It is a key technique of the space experimental system for liquid experiment. The method is especially applicable for unmanned environment as well as non-contact measurement in the experiments.