The invention discloses an organic light emitting device and a main body material of an organic light emitting layer thereof. The molecule of the main body material contains a large steric hindrance group R'. The distance between the molecule of the main body material and the molecule of a doping material is increased through the large steric hindrance group R', so that the distance between excitons is increased, triplet-polaron quenching (TPA) is suppressed, the charge accumulation at an interface of the light emitting layer is reduced, and the occurrence of an efficiency roll-off phenomenonof the device is suppressed.