The effect of the composite hole transporting layer with different polystyrene (PS)-triphenyl diamine (TPD) mass ratios on the performance of organic light-emitting devices (OLEDs) was investigated. By using this blending system as hole transporting layer, a double-layer organic light-emitting device was fabricated with the structure of indium-tin-oxide (ITO)/polystyrene (PS)∶N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD)/ tris-(8-hydroxyquinoline)-aluminum (Alq3)/Mg∶Ag by the spin-coating technique. For comparison, a similar double-layer device was fabricated using pure TPD as hole transporting layer by thermal vacuum deposition method. The hole drift mobility of PS-TPD thin films with different mass ratios was characterized by time-of-flight method, and electroluminescent characteristics of these devices were measured. Results demonstrated that the hole mobility of blending thin films is 1～2 orders of magnitude lower than that of pure TPD film. When the mass ratio is m(PS)∶m(TPD)=10∶90, the device has a maximum luminance of 14280 cd/m2 and a maximum lumen efficiency of 1.2 lm/W. It was concluded that the incorporation of PS with proper concentration will lower the hole mobility of the functional layer, adjust the hole transporting ability of TPD, more effectively balance the number of positive and negative charge carriers in the recombination zone, and thus enhance the luminance and efficiency of the device.