Abstract:International Society for Rock Mechanics (ISRM) proposed two suggested methods for determining rock fracture toughness in 1988 and 1995,respectively. Cracked chevron notched Brazilian disc (CCNBD) suggested by ISRM in 1995 still waits for being perfected. In view of it,two types of marbles are used to make CCNBD and chevron bend (CB) specimen suggested by ISRM in 1988. These specimens are tested on the test machine of MTS810 model. The results of the tests show that fracture toughness value calculated with ISRM suggested method in 1995 is lower than that in 1988,and that fracture toughness value calculated with ISRM suggested method in 1995 are distinctly better after dimensionless stress intensity factor of CCNBD is newly calibrated. The size effect of CCNBD specimens on fracture toughness is discussed based on the cohesive crack model. The geometric shape function is brought forward,which successfully resolve non-similarity problem of CCNBD when using the size effect law proposed by Bazant.