The invention discloses a POSS (polyhedral oligomeric silsesquioxane) enhanced aramid fiber coated membrane for a lithium battery, and a preparation method of the POSS enhanced aramid fiber coated membrane. The preparation method comprises the following steps: (1) mixing POSS, aramid fiber and ionic liquid to obtain POSS/aramid fiber mixed liquid, and adding alkali into the POSS/aramid fiber mixedliquid to adjust the pH value to be more than 4; and (2) coating the single side or double sides of a battery base membrane with the POSS/aramid fiber mixed liquid after the pH is adjusted, putting into a precipitant to separate out and drying. POSS with a cage-shaped pore channel and an inorganic/organic hybrid structure is introduced to serve as inorganic filling particles, and the mechanical strength, the heat stability and the ionic conductivity of the aramid fiber membrane are further improved, so that the electrochemical property is improved; furthermore, the POSS has high biocompatibility, so the coating uniformity and the pore-forming uniformity are improved, the wettability between slurry and the interface of the base membrane is improved, the precipitation time required after coating is greatly reduced and large-scale production is benefited.