  In this paper, a new class of string and holographic dark energy (HDE)
cosmological model in the context of f(R) theory of gravity using the Kasner
metric is considered. The exact solution of filed equations are obtained by
using the relation between average scale factor and the scalar function f(R).
It is observed that the universe is accelerating and expanding. The string
phase of the universe is present at early stage of evolution of the universe.
The universe is dominated by quintessence type HDE at present. Effect of the
curvature function f(R) is also observed on dynamical parameters.
