The present disclosure provides a thermally activated delayed fluorescent material and application thereof, the thermally activated delayed fluorescent material is a compound having a structure represented by Formula I and can be used as a light-emitting layer material of an organic electroluminescent device. The thermally activated delayed fluorescent material is applied to an organic electroluminescent device comprising an anode, a cathode, and at least one organic thin film layer between the anode and the cathode, the light-emitting layer in the organic thin film layer comprises any one or a combination of at least two of the thermally activated delayed fluorescent materials. An energy level difference between the triplet state and the singlet state of the thermally activated delayed fluorescent material provided by the present disclosure can be reduced to below 0.25 eV, and when used as a light-emitting layer material in an organic electroluminescent device, it can improve carrier balance, increase luminous efficiency, and reduce the device's voltage.