The invention discloses a single-lithium-ion-conducting solid polymer electrolyte adopting carbon dioxide based polycarbonate as a main chain and a preparation method of the single-lithium-ion-conducting solid polymer electrolyte. The structure of the electrolyte is as shown in formula (I), M-Li<+> in the formula (I) is COOLi or SO3Li or the like; the number-average molecular weight of the polymer in the formula (I) is 2,000-15,0000 Da, R is (CH2)n, and n is an integer ranging from 0 to 20; the molar percentage of an ion functional group chain segment is included in the formula (I), that is, y / (x+y), is 10%-80%. The prepared polymer single-ion electrolyte has the advantages of being simple and easy to synthesize, environment-friendly, high in room temperature conductivity, high in lithium ion transference number, low in glass transition temperature, good in mechanical strength and film-forming property, wide in electrochemical window, good in thermostability and the like; the electrolyte adopts cheap and available raw materials and has potential application value in lithium batteries, carbon-based supercapacitors, solar cells and the like.