The invention relates to novel polymer electrolyte for a lithium ion battery and a preparation method for the novel polymer electrolyte. A silicon-methoxy-terminated polyether low polymer is taken as a substrate polymer; a boric acid lithium salt can be used as a lithium source and also can catalyze the substrate polymer to realize in situ crosslinking so as to obtain the end group crosslinked polymer electrolyte. The polymer electrolyte has high strength and self-supporting property, high flexibility and relatively wide electrochemical steady window (4.7V); a relatively ideal ionic conductivity (10<-3>Scm<-1>) can be reached by matching with a certain amount of solvent; and in addition, the gel polymer electrolyte is applicable to a power lithium battery and a flexible lithium battery for wearable equipment.