Abstract: It is difficult to fully understand the yield strength of materials under high pressure and high strain rate loading. At present, strength measure under high pressure is mainly based on plate impact technique, in which the effects of strain rate and temperature increase during loading process on material dynamic strength are difficult to resolve. In this work, Lagrangian wave speed and strength of LY12 aluminum under magnetically driven quasi-isentropic compression are studied using CQ-4, a compact strip-line pulsed power generator for isentropic compression experiments. The optimizations of loading electrode and sample configuration, as well as experimental data processing are discussed in detail. Meanwhile, Lagrangian wave speed of LY12 aluminum along loading and unloading path and yield strength under quasi-isentropic compression up to 12GPa are obtained in a good accuracy.