Uneven distribution of water resources in the Chinese remote mountainous region leads to structural water scarcity. The liquid-gas pump system in low drop river environment is an effective solution to this problem, and the vertical downcomer and its involved kinematic characteristics of the gas-liquid two-phase flow are important parts and key technologies to this system. Based on the data under various conditions and the homogeneous flow model above, kinematic characteristics of the gas-liquid two-phase flow in the vertical downcomer are further studied. It is emphasized on the relationships between several factors and a key parameter which can reflect the mixed degree of air and water in the vertical downcomer. The test results were compared with those of the analytical solutions, then the shortcomings of the model and the defects in the experiments are pointed out. In addition, some references and suggestions on choosing design parameters of the diameters of the vertical downcomer are provided.