It is a desolved problem about fluid level in capillary in homogeneous elastic medium on which the seismic p-wave acts. This wave propagates perpendicular to axis of a capillary. In a linear approach the meniscus vibrates with frequency (omega) and amplitude as the same one as a classic oscillator. In the next approximation there is the double frequency oscillation and a direct shift of the meniscus. Thus the fluid level will differ from the static one. After averaging the described solution on the orientations and sizes of capillaries the fluid level is estimated in partly saturated porous medium.