  In this paper, the problem of approximate symmetries of a class of non-linear
reaction-diffusion equations called Kolmogorov-Petrovsky-Piskounov (KPP)
equation is comprehensively analyzed. In order to compute the approximate
symmetries, we have applied the method which was proposed by Fushchich and
Shtelen [8] and fundamentally based on the expansion of the dependent variables
in a perturbation series. Particularly, an optimal system of one dimensional
subalgebras is constructed and some invariant solutions corresponding to the
resulted symmetries are obtained.
