Abstract: The new resin root canal filling materials (NRCFM) were prepared by using thermoplastic elastomer (TPE) and ethylene-vinyl acetate copolymer (EVA) as matrix resin，BaSO_4，fumed SiO₂ and hydroxyapatite (HA) as inorganic fillers and its compositions were emphatically selected and optimized. The stability of NRCFM in artificial saliva with pH 7.0 and 9.5 was also investigated. The results show that the optimal composition of NRCFM is：TPE 30g，EVA 5 g，BaSO₄ 45 g，SiO₂ 10g，HA 10g. NRCFM prepared at this optimal composition has the appropriate mechanical property and excellent resistant-medium stability:  Shore A hardness is 88.9,  tensile strength is 1.99 MPa and elongation at break is 457%. After soaking 30 days in both pH 7.0 and pH 9.5 artificial saliva，mass change of NRCFM is less than 0.5%.