The invention discloses a novel electrolyte compounding mode solid-state lithium battery and a preparation method thereof, and belongs to the technical field of preparation of a lithium battery. A solid-state lithium battery positive electrode comprises a conductive agent, a polymer electrolyte and a positive electrode active material; a negative electrode comprises metal lithium and an alloy thereof; and an electrolyte adopts an inorganic solid-state electrolyte. The preparation method comprises the following steps of enabling a polymer substrate material to be dissolved into an organic solvent and adding a lithium salt, and then adding the positive electrode active material and the conductive agent to be stirred uniformly to obtain composite positive electrode paste; coating an aluminumfoil with the composite positive electrode paste and performing vacuum drying at a temperature of 80 DEG C for 12h to obtain a positive electrode plate; performing repeated casting and drying on the positive electrode plate by a uniform phase mixed solution of the polymer electrolyte to obtain a high-density positive electrode plate; performing stacking treatment and thermal treatment on an inorganic solid-state electrolyte sheet and the high-density positive electrode plate; and putting the negative electrode material on the other side of the inorganic solid-state electrolyte sheet, and performing battery assembling to obtain the solid-state lithium battery. The compaction density of the composite positive electrode prepared in the invention reaches 2.3-3.5g cm<-3>.