Metal transfer mode of the lime titania type structural steel covered electrode is a mixed one that coexists as the globular short-circuiting transfer, the flux-wall guided transfer, the explosive transfer and the spray transfer. Constitute of the metal transfer modes has a direct effect on usability of the covered electrode. Using the Analysator Hannover, the welding electric parameters are measured and analyzed. Four characteristic information values correlated with usability of the covered electrode are extracted, such as the sum of probability density of the short-circuiting voltage, variation coefficient of the arc voltage, the sum of probability density of the big short-circuiting current and the short-circuiting frequency, and then method of the principal component analysis is applied to determining evaluation index of usability of the covered electrode. Usability of the covered electrode is quantitatively evaluated. It offers a new method for scientifically evaluating usability of the lime titania type structural steel covered electrode.