This work investigates experimentally flashing evaporation process of water droplets released into vacuum, particularly on the quantitative characteristics of the process, in order to reveal the influences of the randomicity of the sub-process of nucleation and non-condensable air dissolved inside the liquid. It's clearly shown that nucleation time is a random variable. That may be caused by the following facts that nucleation for ice in high-supercooled water exhibits a strong randomicity and that there exists strong perturbation during quick depressurization. Freezing temperature of liquid droplet is approximately constant after recalescence, which may be determined by the vapor partial pressure at the terminal state. Freezing time is independent of nucleation time, but exhibits an obvious dependence on terminal pressure and drop diameter. Supercooling corresponding to the nucleation is independent of terminal pressure. The averaged values of supercooling at three different terminal pressures of 450, 600 and 1000 Pa are the same, namely 10 K. Furthermore, the influences of non-condensable gases on the process are analyzed and discussed in detail based on the experimental observations. [ABSTRACT FROM AUTHOR]