Wave approach was used to analyze the vibration-isolating performance of approximate equal-mass hollow beam and solid blocking mass,and the effects of thickness and length on the transmission loss of hollow blocking mass were discussed.By designing the simplified model experiment of a flat plate construction with blocking mass,the tested results and theoretical values of transmission loss were compared. As a result,both trends were consistent with each other. The results also showed that the section size had an significant influence on the vibration-isolating performance of hollow-square steel blocking mass within mid and high frequency domain,and approximate equal-mass hollow blocking mass had a more obvious vibration-isolating performance than solid blocking mass within mid and high frequency domain.