High lithium ion conducting 70Li2S·(30− x)P2S5·xP2S3 (mol%) glasses and glass–ceramics were prepared by the mechanical milling method. Glasses were obtained in the composition range of 0≦ x ≦10. The substitution of P2S3 for P2S5 promoted the formation of the P2S6 4− units in the glasses. The conductivity of the glass increased with an increase in P2S3 contents up to 5mol% and the glass with 5mol% of P2S3 showed the conductivity of 1×10−4 Scm−1 at room temperature. In the case of glass–ceramics, the conductivity increased with an increase in P2S3 contents up to 1mol%, and the superionic conducting Li7P3S11 crystal was precipitated in the glass–ceramic. The glass–ceramic with 1mol% of P2S3 showed the highest conductivity of 3.9×10−3 Scm−1 at room temperature.