The compressional sound velocity VP for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of VP (in km/s) on Hugoniot pressure (P, in GPa) can be described by lnVP= 3.079-0.691 ln(P) + 0.094(lnP)2. VP satisfies Birch’s law: VP= 4.068 + 1.677p, where p is corresponding density, which indicated that enstatite is stable throughout the conditions of the lower mantle. The wave velocity P is 0.5% lower and the wave velocity S is 2% higher than that of PREM respectively. We concluded that the lower mantle is mainly composed of perovskite-(Mg1-x, Fex) SiO3 and only a small amount of (Mg1-x, Fex) O is allowed in it. The compressional sound velocity VP for enstatite of polycrystalline specimens were measured at pressures from 40 to 140 GPa using the optical analytical techniques under shock loading. The dependence of VP (in km / s) on Hugoniot pressure (P, in GPa) can be described by lnVP = 3.079-0.691 ln (P) + 0.094 (lnP) 2. VP is Birch’s law: VP = 4.068 + 1.677p, where p is corresponding density, which indicates that enstatite is stable throughout the conditions of the lower mantle. We concluded that the lower mantle is mainly composed of perovskite- (Mg1-x, Fex) SiO3 and only a small amount of (Mg1 -x, Fex) O is allowed in it.