The present invention discloses an encapsulation composition, an encapsulation film including the encapsulation composition, and an electronic device module. The encapsulation composition includes a polymer matrix, a tackifier and a free radical initiator. Based on 100 parts by weight of the polymer matrix, the polymer matrix includes 5 to 100 parts by weight of highly branched polyethylene (P1), 0 to 95 parts by weight of an ethylene-α-olefin copolymer, and 0 to 70 parts by weight of an ethylene-polar monomer copolymer. The highly branched polyethylene (P1) is an ethylene homopolymer having a branch structure and has a degree of branching of not less than 40 branches/1,000 carbon atoms. A density of the ethylene-α-olefin copolymer is not higher than 0.91 g/cm3. The encapsulation composition provided by the present invention has good volume resistivity, aging resistance, processability and low cost.