The invention relates to a 6, 6-dimethyl-6H- benzo [cd] pyrene derivative, which is a class of compounds as shown in a formula (I), wherein n is 1 or 2; R1-R5 are five substituent groups at different positions on Ar, the substituent groups are identical or different from each other, and the substituent groups are respectively selected from H atoms, C1-C20 aliphatic linear chains or branch alkyls or C1-C20 aromatic groups, independently; Ar is an aromatic group; A is N atom or CH; L is a single bond, and is selected from C6-C10 aromatic ring or heteroaromatic ring. The invention also discloses an application of the compounds in organic electroluminescent devices, especially, being used as an electron transport material and/or a luminescent host material of OLED (Organic Light Emitting Diode).