The invention belongs to the technical field of organic optoelectronics, and discloses a sulfur-containing quaternary condensed ring unit and its derivative and a preparation method and an applicationthereof. The sulfur-containing quaternary condensed ring unit has a chemical structural formula shown as the specification, and in the structural formula, X is -C(R1)2-, -NR1-, -Si(R1)2-, -O-, -S-, -(SO)O- or -(CO)O-; R1 is phenyl or C1-4 alkyl; and Y is H, Br or I. The invention also provides the derivative of the sulfur-containing quaternary condensed ring unit. The sulfur-containing quaternarycondensed ring unit and its derivative can be used in an organic light-emitting diode, have a large condensed ring structure, and can increase the thermostability of molecules, and the thermal decomposition temperature exceeds 350 DEG C; the molecule energy grade and band gap can be increased, and molecule aggregation can be inhibited; the sulfur-containing quaternary condensed ring unit has highfluorescence quantum yield, and is in favor of increasing electroluminescent efficiency, conjugation is enhanced, the carrier transmission performance is increased, and the sulfur-containing quaternary condensed ring unit is in favor of increasing the equipment performance.