A transmitting Fabry-Pérot light modulator for display application is proposed. Its optical characteristics are analyzed with multiple beam interference theory. The typical parameters of the light modulator for display are deduced. When the Fabry-Pérot cavity length is λc/4, almost all transmitted light is cut off, the modulator is “off” state. While when the cavity length is 0 or λc/2, corresponding light can transmit the modulator, the modulator is “on” state. It is theoretically proved that this light modulator is capable for display. Finally, one light modulator structure based on micro-electro mechanical system (MEMS) is given. Contrast ratio of this device is 150 by theoretical calculation. Result of the software simulation shows that this structure has as low as 2.4 V actuating voltage.