Abstract: Wetting correlations between rosin & other 6 flux components and Sn-9Zn/Cu are studied based upon uniform design method. The factors rosin, ZnCl₂, NH₄Cl, ethylene glycol, oleic acid and lactic acid, were divided into three groups and twelve levels in the experiment. By using computer software UST4.0, the wetting spread area were processed statistically and three correlative equations were obtained. The results showed that the effect of ZnCl₂, oleic acid and the mutual term of ZnCl₂& NH₄Cl were positive. The effects of NH₄Cl was negative, and that of rosin with ZnCl₂ or NH₄Cl together is little, ZnCl₂ or oleic acid is also in quadratic & negative form. The analysis of variance showed that the multinomial equations were sound and meaningful.