A novel designed method for tunable wavelength microcavity organic electroluminescent diode (MOLED) based on the birefringence of liquid crystal was presented. By modulated the refractive index of liquid crystal, the device could radiate with different wavelength continuously. The simulated result showed that the tunable range could reach to 60 nm and the full width of half maximum is 5.5 nm. The device could be applied to wavelength converter and tunable light source.