Abstract: Graphite core structure contains pebble bed core, which is a key part of high temperature gas-cooled reactor. The dynamic response and structural integrality were studied under kinds of loads, especially earthquake, to meet the requirement of long term safe operation and sound design. The seismic test program on double-layer graphite core model, which is the part of HTR-PM side reflector structure, was carried out. Dynamic behavior including frequency response, acceleration, flexibility and bricks relative displacement were recorded. The keys and dowels stress, strain and destroy were analyzed. The important influencing factors were discussed by test and simulation results comparison. The experience obtained by the seismic test can improve the future more complicate graphite core structural seismic model research.