Based on the layer-optimized method, the devices of sandwiched structure are pr oduced by compounding MEH-PPV and SiO2 In three different voltage regions of alternating current, the devices luminesce differently. When the voltage is low, red emission is obtained; and if the voltage is high, blue emission is acquired. The superposition of the above two emissions is obtained when the voltage is moderate. The red or blue emission belongs to the solidstate cathodoluminesc ence, it originates from the accelerated electrons in SiO2, which bombard the organic layers. By the study on the optic characteristics of the devices, the sc opes and regulations of spectra shift are analyzed.