At present, liquid organic carbonate electrolyte is commonly used in lithium secondary batteries, which is prone to leakage, combustion, and even explosion. Polymer solid state electrolyte exhibits the advantages of light mass, good machinability and good compatibility with electrode interface, which can overcome the defects of traditional liquid electrolyte effectively. It presents a very important application prospect in solid state lithium battery field. Poly(ethylene oxide) (PEO) solid state electrolyte is one of the earliest studied and most widely used polymer solid electrolyte systems. In this paper, the current status of PEO polymer solid state electrolyte was reviewed, focusing on four modification strategies based on ionic conductivity modification, electrochemical window modification, mechanical strength modification and flame retardant property modification. Finally, the development trend of PEO polymer solid state electrolyte was prospected.