The invention provides modified polyether and a preparation method and application thereof. The modified polyether is as defined in the description that n is an integer selected from 10-75. The modified polyether is high in solubility in CO2, low in raw material preparation cost and simple in preparation technology, and types of pro-CO2 polymers are expanded; serving as a pro-CO2 polymer segment, the modified polyether can be developed into a surface active agent, a chelating agent, a dispersing agent, a thicker or a CO2 adsorbent and applied to a liquid or supercritical CO2 system, and wide application potential is achieved.