We fabricated blue phosphorescent organic light-emitting devices of A and B groups by using B3PyPPM as electron transport layer and TCTA and mCP as host. The structure are: ITO/HATCN(5 nm)/TAPC(45 nm)/TCTA∶FIrpic(15%,15 nm)/B3PyPPM(X nm)/B3PyPPM∶Cs(15%,10 nm)/Al and ITO/HATCN(5 nm)/TAPC(45 nm)/mCP(5 nm)/mCP∶FIrpic(15%,15 nm)/B3PyPPM(X nm)/B3PyPPM∶Cs(15%,10 nm)/Al. The values of X are 40 nm, 45 nm, 50 nm, and 55 nm, respectively. Experiments show that the devices which use mCP as host is far better than the device using TCTA as host. The maximum luminance of 14 930 cd/m2 and the maximum current efficiency of 9.9 cd/A are obtained. The efficiency roll-off in EQE is only 10.1% when the luminance rises from 500 cd/m2 to 3 000 cd/m2. Since B3PyMPM can improve the injection characteristics of electrons, the turn-on voltage of the two groups devices are 2.3 V and 2.8 V, respectively, which is lower than the Firpic blue phosphorescent OLEDs fabricated with other electron transport layer materials. At the current density of 30 mA/cm2, the spectra of all devices have a major peaks at 474 nm and a vibrational peak at 496 nm. As the thickness of B3PyPPM increases, the intensity of the shoulder increases due to the microcavity effect. The microcavity phenomenon existing in the device is studied in detail by optical simulation.