Martian meteorites provide direct evidence and criticalconstraints on the evolution of the Martian mantle. Olivine-phyricshergottites are suggested to carry geochemical information of the primitiveMartian mantle. Detailed petrological and mineralogical analyses were madefor the NWA (Northwest Africa) 8716 olivine-phyric shergottite which is composed of largeolivine megacrysts (0.5--1.8 mm) set in a matrix of relatively smallolivine (50--400 $\upmu $m), and pyroxene with interstitialmaskelynite, and other accessory minerals. Both the melt inclusion withinolivine phenocryst and the calculated bulk rock display an LREE (Light Rare Earth Element)-depletedpattern ([La/Yb]$_\textCI$ 0.06 to 0.1) which is in concordant with some otherolivine-phyric shergottites. This indicates NWA 8716 is derived from adepleted Martian magma. The origin of olivine megacrysts is a crucial factoron whether NWA 8716 can be counted to represent composition of a primitive,mantle-derived magma. The crystal size distribution analysis indicatesexcesses of large crystals which may be due to the entrainment of cumulates.Calculations of Fe-Mg and rare earth element partition reveal that NWA 8716did not crystallize in a closed system. But estimated compositions of theparent melt are not in large discrepancy with what observed, indicating themegacrysts crystallized from a magma similar to its parent melt. NWA 8716should have derived from a less evolved depleted reservoir.