The invention relates to an indenofluorene-based conjugated polymer laser gain material, a method for preparing the same and application of the indenofluorene-based conjugated polymer laser gain material. Indenofluorene structures are used as frameworks for the indenofluorene-based conjugated polymer laser gain material, different receptor structures are selected, copolymerization is carried out to obtain trapezoidal block copolymers, a general structural formula of the trapezoidal block copolymers is shown, an R in the general formula I represents one of alkyl, alkoxy, alkyl phenyl and alkoxy phenyl of C1-C30, and an A represents electron receptor structure modification units. The indenofluorene-based conjugated polymer laser gain material, the method and the application have the advantages that the indenofluorene-based conjugated polymer laser gain material is low in cost, high in yield and good in solubility, and synthesis is simple and controllable; the indenofluorene-based conjugated polymer laser gain material is good in heat stability, reversible in oxidation-reduction characteristic and excellent in film-forming properties, and film devices can be prepared by the aid of simple solution film-forming modes; the indenofluorene-based conjugated polymer laser gain material is high in brightness and excellent in luminescence efficiency when used as an active luminescence layer in organic electroluminescent devices, is low in laser threshold and high in gain when applied to organic laser devices and is a luminescent material system with important application prospect.