In foundation vibration control， the shallower single open trench has an unsatisfactory vibration isolation effect due to its low scattering efficiency. As one of the countermeasures， multiple open trenches can achieve the ideal vibration isolation effect by improving the scattering efficiency. According to the basic theory of elastodynamics， the wave function expansion is carried out in the complex number domain. The governing equations of the problem are established from the free boundary conditions of the stress around the hollow trench and with the help of conformal mapping theory and multi-polar coordinate transformation technology， the analytical solution to plane P-SV wave scattering is given. Taking double open trench as an example， the effects of excitation frequency， cavity length and cavity spacing on vibration isolation are analyzed. The results show that the vibration isolation effect of double open trenches is better than that of single open trench. With the increase of cavity length， the vibration isolation effect is better. The existence of certain open trench spacing makes vibration isolation effect of double open trenches better.