Recently,　a　new　concept　called　multiplicative　differential　was　introduced　by　Ellingsen　et　al.　[7].　As　an　extension　of　the　differential　uniformity,　it　is　theoretically　appealing　to　determine　the　properties　of　c-differential　uniformity　and　the　corresponding　c-differential　spectrum.　In　this　paper,　based　on　certain　quadratic　character　sums　and　two　special　elliptic　curves　over　F-p,　the　(-1)-differential　spectra　of　the　following　two　classes　of　power　functions　over　F-p(n)　is　completely　determined:　(1)　f(1)(x)=x(pn+3/2),　where　p＞3　and　p　equivalent　to　3(mod4);　(2)　f(2)(x)=x(pn)-3,　where　p＞3.　The　obtained　result　shows　that　the　(-1)-differential　spectra　of　f(1)(x)　and　f(2)(x)　can　be　expressed　explicitly　in　terms　of　n.　Moreover,　an　upper　bound　of　the　c-differential　uniformity　of　f(2)(x)　is　given.