There is a lack of detection means for the isolation performance of the buildings built by passive control technology， so it is of great significance to test the dynamic characteristics of the isolated structures on the spot. A 4-story base isolation kindergarten was tested in the field， and the test device， method and results were displayed. The results were compared with the seismic struc? ture model under the same conditions， and the dynamic response law and damping effect of the actual isolation structure were ex? plored. The building was pushed away with hydraulic jack to produce 98 mm （corresponding to LNR500 shear strain 102%） hori? zontal initial displacement of the isolation layer， and concrete jacking rod was installed to support the building； The concrete rod was blasted with explosives and unloaded instantly to make the building vibrate freely； The dynamic response and other parameters were tested and analyzed. The results show that under the condition of horizontal initial displacement， the first-order natural vibra? tion period of the isolated structure is significantly longer than that of the seismic structure， and the damping ratio increases； The hysteretic curve of the isolation layer is full； The dynamic response control effect of each floor is obvious， but the acceleration of the roof floor is slightly amplified compared with that of the bottom floor； After unloading， the isolation layer instantly resets， which shows that the isolation layer has rapid reset performance.