Abstract: This paper studies the problem on free vibration of cantilever beam acted by liquid on two sides. The exact calculating formulae of mode shape functions and natural frequencies of free vibration of cantilever beam are given when the heights of liquids on two sides of cantilever beam are unequal. The results can be abtained by the use of computer. The analysis shows that the effect of liquid on free vibration of cantilever beam is equivelent to a generalized distributive mass attached on the beam.