Abstract: This paper aims to study the influence of geometric parameters of rectangular trench on the vibration isolation effect of the area behind the trench. The amplitude of acceleration at the corresponding control point when the free foundation and rectangular trench are measured respectively through field tests. The two-dimensional plane contour map about the ratio of the two are drawn. The area with a ratio less than 0.4 is taken as the vibration shielding area. The vibration shielding area is taken as the evaluation index of vibration isolation effect. The following conclusions are drawn through the research. Energy redistribution can occur when Rayleigh waves meet rectangular trench in the process of propagation. Part of Rayleigh waves can break through the barrier of trench and continue to propagate forward,while the other part can be bounced back by rectangular trench and propagate backward. When the ratio of rectangular groove depth to Rayleigh wave length is 0.08~0.53,increasing the ratio can significantly increase the vibration shielding area. But when the ratio is 0.53~0.75,it has little influence on the vibration shielding area. The ratio of rectangular trench width to Rayleigh wave length has little influence on the vibration shielding area. When the ratio of rectangular trench length to Rayleigh wave length varies within the range of 1.11~1.52,the vibration shielding area does not change significantly. When the ratio of the rectangular trench source distance to the Rayleigh wave length is 0.78~1.13,the change of the ratio has little influence on the vibration shielding area. When the normalized cross-sectional area of the trench varies from 0.02 to 0.78,it has a significant effect on the area of the vibration shielding area.