On the basis of Rolle′s theorem in the calculus

a suff icient condition for two polynomials being equivalent was proved.Furthermore

t he necessary and sufficient conditions for two n-colorable graphs of order n+s(s

n∈Z+) being chromatic equivalent was given by chromatic n umber

girth and subgraph number of complement graph.The conclusion provided ne w approaches for constructing chromatic equivalent graphs.Then by these new met hods

some new classes of chromatic equivalent n-colorable graphs of order n+3 were obtained.