The organic thin film optical microcavity electroluminescent (TFEL) devices with aluminium doped zinc oxide (AZO) transparent conducting thin film as anode have been fabricated. Some effects of vertical Fabry—Perot microcavity on spotaneous emission of organic TFEL devices have been observed. These optical mierocavity effects are spectral narrowing, enhancement of emission intensity and angle dependence of emision. The half width of electroluminescent spectra of organic TFEL device with mierocavity structure iS about 14 nm while that of ordinary device without cavity structure is about 100 nm. The emision intensity of the devices with cavity structure is higher than that of device without cavity structure. The emission peaks of cavity devices are shifted to blue side by increasing the detection angle. Different colors ate obtained by changing the thickness of AZO layer or inserting different thickness of filler layer TiO2.