Abstract: Objective To study the correlation between OD450 value and viable number of Staphylococcus aureus（S.aureus）.Methods A single colony of S.aureus was cultured in LB liquid medium for 18h,and OD450 value was detected after preliminary dilution of the bacterial suspension.Corresponding OD450 values were detected once again by further diluting the bacterial suspension if the OD450 value was set at 0.9-1.0.Finally,the viable number of S.aureus was calculated by counting the plate colonies after the bacterial suspension was diluted 5×10⁵ times,and 0.5ml bacterial suspension was cultured for 18h in LB agar plates.Results The OD450 value（X） was linearly correlated with the viable number of S.aureus（Y×10⁸/ml）,which could be expressed by the linear regression equation: Y=1.153 92X+0.007 68.Conclusion It is a convenient,accurate and rapid method to detect the viable number of S.aureus in bacterial suspension using the OD450 value.