The invention belongs to the technical field of OLED, and provides a compound used as a host material. The compound has a structure as shown in a formula (I) which is described in the specification. In the formula (I), X is selected from the group consisting of C, O, S, Se, Si and Te atoms; a and b respectively represent the number of an electron donor D and an electron acceptor A and are respectively selected from the group consisting of 1, 2 and 3; c and d are respectively selected from the group consisting of 0, 1 and 2; L1, L2 and the electron donor D are respectively and independently selected from the group consisting of an alkyl group, a cycloalkyl group, a heterocyclic group, an aryl group, a heteroaryl group, a fused aryl group and a fused heteroaryl group; and the electrozxn acceptor A is selected from the group consisting of an azacycle-containing substituent, a cyano-containing substituent, a phosphoxy-containing substituent and a triaryl boron substituent. The compound provided by the invention has a D-(pi)-sigma-(pi)-A structure with bipolarity, and a sigma bond can effectively interrupt the intramolecular charge transfer between the electron donor D and the electronacceptor A, and limits an excited state to be a local excited state in a segment of D or A, so the compound has a dipole moment with a small excited state; and when the compound is used as the host material of a luminescent layer, the compound can effectively reduce the efficiency roll-off of a blue light material and improves luminescent brightness and luminescent efficiency.