The present invention provides a blue light thermally activated delayed fluorescence (TADF) material, a preparation method thereof, and an electroluminescent device. The blue TADF material achieves high luminous efficiency and TADF efficiency to realize excellent solubility by attaching an alkyl chain for increasing solubility to a periphery of the blue light TADF material, and by attaching a tert-butylcarbazole unit having a high energy state to an end of the alkyl chain of the blue light TADF material, thereby allowing the material to be processed by solution spin coating, and the terminal carbazole can act as a host, enabling non-doping of a luminescent layer while effectively avoiding phase separation.