The invention provides an organic electro-phosphorescent material and a preparation method thereof, and an organic electroluminescent device. The invention provides the organic electro-phosphorescent material with the general formula (P), wherein R is C1-C20 straight-chain or branched-chain alkyl, or hydrogen atom. The organic electro-phosphorescent material is an organic electro-phosphorescent material iridium metal complex synthesized with 2-(2',4'-difluoro-3'-cyanophenyl)pyrimidine as a cyclo-metal main ligand and with 5-(2'-pyridyl)-1,2,3,4-tetrazole as a subsidiary ligand. The adjustment upon material luminescent colors is realized through introducing alkyl chain chemical modification to the pyrimidine ring of the cyclo-metal main ligand, such that phosphorescent emission with bluer emission wavelength is obtained.