Abstract: We studied material strength at high pressure ( more than 10 GPa) and high strain rates (106-108 s-1) in Al using the Shenguang Ⅲ prototype laser facility. The Al sample was maintained well below the melting temperature using a quasi-isentropic ramped drive based on a reservoir-gap-sample configuration. To measure the RT ripple growth, we used face-on radiography with a 4.7 keV laser driven Ti X-ray backlighter. This paper would show detailed designs and achieve the RT growth factors at different times. In the experiment, continuous phase plates (CPP) were used to improve the focus beam quality. The results show that CPP can effectively improve the uniformity of driven beam and the backlighter beam. Finally the experimental results reveal that the method to infer material strength by measuring RT instability growth is feasible at Shenguang Ⅲ prototype laser facility.