The feasibility of evaluating the performance of anti-agglomerants from analyzing the variation of morphologies and chord length of particles was examined using an autoclave installed with a particle video microscope and focused beam reflectance measurement probes. The experimental results from methane + water + diesel oil systems show that the agglomeration of hydrate can be judged directly from two laser probes. With the action of an effective anti-agglomerant, the size of droplets/hydrate particles is uniform and tends to that before hydrate formation when most water converts to hydrate or the system stops stirring for 9 h, although the agglomeration occurs when water droplets initially convert into hydrates. The evaluation method was examined under different anti-agglomerant concentrations, water cuts, and subcoolings for water + diesel oil systems. The action mechanism of anti-agglomerants was also proposed.