The Wadi Bayhan mafic-ultramafic intrusions associated with magmatic PGE-bearing Cu-Ni sulphide deposit are located in the south margin of the Arabian-Nubian Shield，SW Yemen． The intrusions consist of dunite， olivine-pyroxenite，lherzolite，hornblendite，gabbro and gabbronorite． The dunite and lherzolite are the main host rock for the Cu-Ni ores． The new data of the chemical compositions of the rocks have SiO2 ( 50%- 53. 6%) ，Al2O3 ( 0-32%) and MgO ( 4%-28%) ，and relatively low TiO2 ( 0-3. 2%) and K2 O + Na2O ( 0. 04% － 5. 2%) ． The geochemical characteristics indicate that the parental magma is high-magnesium tholeiitic． Sulfur had reached saturation and immiscible sulfides droplets segregated from silicate magmas before their emplacement．