The technique of monitoring radon concentrations in groundwater has been used for earthquake prediction for nearly half a century. However, the upgrading of radon-monitoring devices has been very slow. Currently, the FD-105K electrometer and FD-125 radon-thorium analyzer are the most commonly used devices for measuring radon concentrations in water, but measurement errors may occur because the bubbling process is artificially conducted and the measured data are read by visual observation. This study presents an experimental study of the AlphaGUARD P2000 portable radon monitor, a more advanced device that can automatically perform the bubbling process and read data, avoiding errors caused by manual operation. The improved accuracy of this radon monitor helps to better detect radon anomalies prior to earthquakes. The AlphaGUARD P2000 is portable, battery-powered, and easy to use. It can be used in field observations, verification of anomalies, and measurements of radon concentration in soil for the observation of seismic subsurface fluids.