With the development of the space industry, space liquid management become one of the important techniques in realizing in-orbit refueling of the spacecrafts, and free surface flow stability is the critical problem in this field. The experiment set-up is designed for microgravity fluid transport study with two channels. In the experiments, symmetrical channel and asymmetrical channel with identical open length for comparison are used, and 10 experiments in the drop tower of Chinese Academy of Sciences are performed. By analyzing the free surface characters, it is found that there exist three typical flow patterns: subcritical, supercritical and critical. Meanwhile, the critical flow rate is obtained. Finally, the free surface flow characteritics of two different channels are compared.