Taking the BMG series as a material system, the physi ca l and structural parameters of the BMG were separately calculated by the additio nal principle, including mixed entropy S mix , mole atomic radius differ ence εd, mole atomic electronic difference εe, thermal diffusion ratio α and ratio （T m/H m） of melting point temperature T m and me lting enthalpy H m. R c（critical cooling velocity）, Z max （ maximum size） and Z max /R c for BMG were considered as the targe t of glass forming abil ity respectively. The statistic figures ε d·ε e ·α·S mix ·T m/H m （denoted by Л）: R c,-Л, Z max -Л ,Z max /R c-Л have been drawn by Origin 6.1 software. The re sults showed that the optimum GFA for Л=0.020～0.175, for Л=0.047～0.1 50 and for Л=0.03～0.15 when R c,Z max and Z max /R c as were taken as the target respectively. The range of c omprehensive optimum Л is 0.047～0.15. It was concuded that the Л was an ideal new paramete r to characterise the glass forming ability of the BMG.