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Strategy of Sb-substitution is carried out on the template structure Na4Sn0.67M0.33S4 (M =Si,Ge),which affords a series of quinary sulfide-based sodium fast ionic conductors formulated as Na4-x[Sn0.67M0.33]1-xSbxS4 (M =Si,x=0.1.0.2,0.3;M =Ge,x =0.2.).Among them,the highest ambient ionic conductivity (1.75 × 10-4 S cm-1) is achieved when M =Si and x =0.2.The new fast ionic conductor Na3.8[Sn0.67Si0.33]0.8Sb0.2S4 is isostructural to its structure template Na4Sn0.67Si0.33S4 and thus crystallizes in the space group of I41/acd.It is shown that the incorporation of Sb improves the ionic conductivity.The study of lattice parameters shows that the improvement of the ion conductivity by Sbsubstitution is mainly due to the enlarged crystal lattice.Furthermore,using Na3.8[Sn0.67Si0.33]0.8Sb02.S4 as solid electrolytes,room temperature all-solid-state sodium battery of Se0.05S0.gs@pPAN/Na3Sn is realized,which proves the novel fast ionic conductor a potential candidate to apply in sodium solid state battery.This work not only extends the scope of Na4[Sn0.67Si0.33]S4,the I41/acd space group template,but also deepens the understanding of the lattice size effect on the structure and property relationship by aliovalent substitution.