The transition metal complexes with phosphido bridge have been widely used insynthesis of organometallic compounds. The NMR 31P chemical shift is useful in structureelucidation. The value of 31P shift ofter used as a structural probe for the presence orabsence of metal-metal bond. In this paper,the 31P shift of the series of compound[(CO)4M(μ-PMe2)]2, M=V, Cr, Mn have been calculated. The correlation of 31P shiftwith metal-metal bond has been studied.In this paper "Magnetic nuclei molecular orbit group approximation for calculationof NMR chemical shift" has been proposed.