Abstract: The influences of carbon fiber and polypropylene fiber on fracture toughness of high performance cement mortar containing 30% of fly ash or 10% of silicon powder are studied in the compact tensile test.The crack-resistance and toughening mechanism of fiber-enhanced mortar are analyzed.Test results show that the carbon fiber with high elastic modulus can not only improve strength performance but also improve toughness of cement mortar,and that the polypropylene fiber with low elastic modulus can only toughen cement mortar.