Abstract
We consider a class of generalized Steffensen's methods for solving nonlinear equations without any derivative. We establish successful the existence-convergence theorem of generalized Steffensen's iteration under the Kantorovich-Ostrowski's conditions and present an upper bound, but it is not optimal. These conclusions contain the special case of Steffensen's method [6]. In the mean time, we compare the accurate error bound of Newton's method with error bounds of generalized Steffensen's methods, we show that latter is less than former.