In this paper， a method for calculating the vibration response of beams damped with constrained damping layer is present? ed. The indoor vibration experiment of I-beam was carried out， and the vibration response at different positions was measured. A numerical simulation model was established simultaneously based on the finite element method， and the natural frequencies and modal loss factors of I-beam were calculated accurately by using the modal strain energy method. Based on the above results， the modal superposition method was used for the harmonic response analysis， and the vibration response of the I-beam damped with constrained damping layer was obtained. The accuracy of the model was verified by comparing the measured and simulated results. The effects of design parameters （damping layer thickness and constrained layer thickness） on the natural frequency， modal loss factor and overall vibration acceleration level were analyzed. The results show that the vibration response of each component has a similar change rule. The overall vibration acceleration level of web is the largest， followed by the bottom， and the roof is the small? est. In general， the thickness of damping layer has little effect on the first 5 order natural frequencies of I-beam， but with the in? crease of the thickness of constrained layer， the first 5 order natural frequencies of I-beam decrease first and then increase. Increas? ing the thickness of damping layer and constrained layer can continuously improve the modal loss factor of I-beam， thereby reduc? ing the overall vibration acceleration level effectively， and the vibration reduction effect of web is better than that of roof and bot? tom.