Schiff base platinum（Ⅱ） complexes are considered to be a promising red phosphorescent organic light-emitting diode（OLED） material in biomedical display，telecommunication security and other fields due to their stability，modifiability and easy synthesis．However，they often leads to some problems such as low photoluminescence quantum yield（PLQY） and low device performance caused by aggregation quenching due to their obvious structural planarity．Introducing groups with larger steric hindrance at the periphery of the Schiff base may effectively improve the above problems．In this study，the corresponding ligands were synthesized and further coordinated with K,2,PtCl,4, under alkaline conditions to synthesize two novel Schiff base platinum（Ⅱ） complexes SPtA and SPtB with peripherally introduced large sterically hindered phenyl groups．The compounds were characterized by nuclear magnetic resonance（NMR） and high-resolution mass spectrometry（HRMS）. Theoretical calculations for the compounds were performed using time-dependent density functional theory （TDDFT）．The thermodynamic properties of the compounds were studied by thermogravimetric analysis（TGA） and differential scanning calorimetry（DSC）．The electrochemical properties of the compounds were determined by cyclic voltammetry（CV）．Meanwhile，the optical properties such as absorption and emission spectra，PLQY，and phosphorescence lifetime of the compounds were studied．Using SPtB as the doped guest material，a series of devices were fabricated by vacuum evaporation method to study the optoelectronic properties．The results showed that the thermal decomposition temperatures（,T,d,） of SPtA and SPtB are 395 ℃ and 420 ℃，which are higher thermal decomposition temperatures，while the maximum emission wavelengths are both 632 nm，and PLQYs were 45% and 47%，which were higher than those of reference molecule. In the following device studies，the effects of the host，thickness，and guest doping ratio of the light-emitting layer on the device performance were compared．Finally，with tris（4-carbazoyl-9-ylphenyl）amine （TCTA） and 1，3，5-tri（m-pyrid-3-yl-phenyl）benzene （TmTyPB） as mixed hosts，the thickness of the light-emitting layer was 30 nm，the doping concentration of SPtB was 3%，and the optimal device structure was obtained．It had a maximum current efficiency of 10.5 cd/A，a maximum power efficiency of 7.2 Im/W and a maximum external quantum efficiency（EQE） of 9.6%．The maximum emission wavelength of the device was maintained at 630 nm under different voltages，and the CIE coordinates were （0.64，0.35），which was a red phosphorescent OLED device with high color purity．Studies showed that the introduction of large sterically hindered phenyl groups at the periphery of Schiff base platinum（Ⅱ） complexes could reduce molecular aggregation and improve molecular performance．