Green phosphorescent microcavity organic light-emitting devices (MOLEDs) in a architecture of Glass/DBR/ITO/MoO3(1 nm) /TcTa(40 nm)/ CBP:Ir(ppy)3(40 nm,6%)/TPBI(47 nm)/LiF(1 nm)/Al(80 nm) using typical green phosphorescent Ir(ppy)3 as luminous layer, DBR and Al as a pair of reflector of microcavity are fabricated. For comparison, OLED without cavity is also developed to investigate the effect of microcavity structure on luminescent properties of phosphorescent devices. The peak of electroluminescence (EL) spectrum of OLED is 510 nm, and the full-width at half-maximum (FWHM) is 70 nm. The peak of MOLED is 514 nm and the FWHM is 35 nm.The FWHM of MOLED is reduced by half for the OLED without microcavity. Compared with the EL spectrum of non-cavity OLEDs, the linewidth of MOLED is narrowed. Also, the colour purity of MOLED is improved. For MOLED, the maximum brightness and the maximum current efficiency are 143000 cd/m2 and 64.4 cd/A, respectively. The maximum brightness and current efficiency of OLED are 103000 cd/m2 and 41.6 cd/A. The maximum external quantum efficiency (EQE) of the device is tested and calculated, and the maximum EQEs of MOLED and OLED are 18.6% and 14.3% , respectively. The experimental results show that the luminescence properties of microcavity devices are improved greatly compared with that of the no-cavity devices.