Abstract: This paper makes a comprehensive discussion of the well-aquifer system and water level observation system, and from the oscillation theory, has developed the oscillation equations with two degrees of freedom for these two systems. With the possible solutions to this set of equations, this paper discusses the factors that affect the response of these two systems to seismic waves and earth tides. It is considered that the above-mentioned response mainly depends on the intrinsic periods of these two systems. Theoretical analysis shows that, as to seismic waves, as the aquifer's transmissibility gets greater, the effective height of the well water column get bigger, the equivalent mass of the observation instruments gets larger, the radius of the buoy section gets bigger and the radius of the well casing section gets smaller, the amplification of the system's response gets larger. But these factors exercise small effect on the response of earth tides of long periods. It is also pointed out that under certain circumstances the period of the water level observation system may play an important role, which should not be neglected in research and analysis.