It is an ideal selection to use a-Si:H film, which is cheap and with small lag, as the photoconductive layer of liquid crystal light valve. By using the method of impedance matching, an a-Si:H liquid crystal light valve is designed and fabricated, and the clear image on a large screen projective system is obtained. The resolution of the valve is 201p/mm. The sensitometry measurement shows that the projection light level varies linearly with the writing light level when the latter is below 100W/cm2. The measurement of transient response at the writing light level of 100W/cm2 indicates that the rise time is 60ms and the decay time is 80ms.