The nematode Caenorhabditis (C.) elegans has been widely used as a model animal for fundamental biological research. In order to investigate the effect of exercise on degenerative behaviors of C. elegans, such as physiological (lifespan, progeny) and biomechanical (propulsion, total power and swimming gait) properties, we developed a flow visualization technique to characterize the motility of C. elegans. Quantifying the motility of micro-organisms is always essential in understanding their biomechanical properties. Up to date, however, the direct measurement of the motility of C. elegans remains a big challenge due to lack of proper tools. Therefore, a simple image-based algorithm using a microparticle image velocimetry (μPIV) for deriving the kinetic power and propulsive force of the nematode C. elegans was developed in this study. For the measurement, each worm was confined in a 0.5 μL droplet which was sandwiched between two glass slides separated by two tapes. The motility of the confined worm was derived from the fluid motion according to the law of conservation of energy. The experimental result showed that our measured values appear to be in good agreements with the prior data. The image-based algorithm was proven to be a simple and automated measure for characterizing the dynamic motility of micro-swimmers. The study will eventually provide valuable information for treating and preventing degenerative diseases in higher animals.