According to the static fracture toughness test method using short bar specimen presented by both American Society for Testing and Materials (ASTM) and International Society for Rock Mechanics (ISRM), the rectangular double beam (RDB) specimen for dynamic rock fracture toughness (KId) test was introduced. Split Hopkinson pressure bar (SHPB) was used to get the tensile loading at the crack tip of specimen by incident bar impacting the end surface of the specimen. Strain gauges were attached on the incident bar and transmitter bar to get the strain voltage change of the incident wave, reflection wave and transmission wave, and strain gauges were also attached near the crack tip of the specimen to get the time interval from the beginning of loading to the crack initiation. Then the incident wave, reflection wave and transmission wave were used to calculate the loading history, which was put into the finite element model to calculate the history of the stress intensity factor KI, and the dynamic fracture toughness (KId) was determined with the crack initiation time. The dynamic facture toughness of marble was 2.6 MPa·m1/2 when the loading rate was 1.68×104 MPa·m1/2s-1.